A rootkit is a collection of
computer software
Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work.
At the lowest programming level, executable code consists ...
, typically malicious, designed to enable access to a computer or an area of its software that is not otherwise allowed (for example, to an unauthorized user) and often masks its existence or the existence of other software.
The term ''rootkit'' is a
compound
Compound may refer to:
Architecture and built environments
* Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall
** Compound (fortification), a version of the above fortified with defensive struc ...
of "
root" (the traditional name of the privileged account on
Unix-like operating systems) and the word "kit" (which refers to the software components that implement the tool). The term "rootkit" has negative connotations through its association with
malware.
Rootkit installation can be automated, or an
attacker
In some team sports, an attacker is a specific type of player, usually involved in aggressive play. Heavy attackers are, usually, placed up front: their goal is to score the most possible points for the team. In association football, attackers ...
can install it after having obtained root or administrator access. Obtaining this access is a result of direct attack on a system, i.e. exploiting a vulnerability (such as
privilege escalation) or a
password
A password, sometimes called a passcode (for example in Apple devices), is secret data, typically a string of characters, usually used to confirm a user's identity. Traditionally, passwords were expected to be memorized, but the large number of ...
(obtained by
cracking or
social engineering tactics like "
phishing"). Once installed, it becomes possible to hide the intrusion as well as to maintain privileged access. Full control over a system means that existing software can be modified, including software that might otherwise be used to detect or circumvent it.
Rootkit detection is difficult because a rootkit may be able to subvert the software that is intended to find it. Detection methods include using an alternative and trusted
operating system, behavioral-based methods, signature scanning, difference scanning, and
memory dump
In computing, a core dump, memory dump, crash dump, storage dump, system dump, or ABEND dump consists of the recorded state of the working memory of a computer program at a specific time, generally when the program has crashed or otherwise termina ...
analysis. Removal can be complicated or practically impossible, especially in cases where the rootkit resides in the
kernel
Kernel may refer to:
Computing
* Kernel (operating system), the central component of most operating systems
* Kernel (image processing), a matrix used for image convolution
* Compute kernel, in GPGPU programming
* Kernel method, in machine learni ...
; reinstallation of the operating system may be the only available solution to the problem. When dealing with
firmware rootkits, removal may require
hardware replacement, or specialized equipment.
History
The term ''rootkit'' or ''root kit'' originally referred to a maliciously modified set of administrative tools for a
Unix-like operating system that granted "
root" access.
If an intruder could replace the standard administrative tools on a system with a rootkit, the intruder could obtain root access over the system whilst simultaneously concealing these activities from the legitimate
system administrator
A system administrator, or sysadmin, or admin is a person who is responsible for the upkeep, configuration, and reliable operation of computer systems, especially multi-user computers, such as servers. The system administrator seeks to en ...
. These first-generation rootkits were trivial to detect by using tools such as
Tripwire
A tripwire is a passive triggering mechanism. Typically, a wire or cord is attached to a device for detecting or reacting to physical movement.
Military applications
Such tripwires may be attached to one or more mines – especially fragme ...
that had not been compromised to access the same information.
Lane Davis and Steven Dake wrote the earliest known rootkit in 1990 for
Sun Microsystems'
SunOS UNIX operating system. In the lecture he gave upon receiving the
Turing award
The ACM A. M. Turing Award is an annual prize given by the Association for Computing Machinery (ACM) for contributions of lasting and major technical importance to computer science. It is generally recognized as the highest distinction in comput ...
in 1983,
Ken Thompson of
Bell Labs
Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984),
then AT&T Bell Laboratories (1984–1996)
and Bell Labs Innovations (1996–2007),
is an American industrial research and scientific development company owned by mult ...
, one of the creators of
Unix, theorized about subverting the
C compiler
This page is intended to list all current compilers, compiler generators, interpreters, translators, tool foundations, assemblers, automatable command line interfaces ( shells), etc.
Ada Compilers
ALGOL 60 compilers
ALGOL 68 compilers
cf. ...
in a Unix distribution and discussed the exploit. The modified compiler would detect attempts to compile the Unix
login
command and generate altered code that would accept not only the user's correct password, but an additional "
backdoor
A back door is a door in the rear of a building. Back door may also refer to:
Arts and media
* Back Door (jazz trio), a British group
* Porta dos Fundos (literally “Back Door” in Portuguese) Brazilian comedy YouTube channel.
* Works so tit ...
" password known to the attacker. Additionally, the compiler would detect attempts to compile a new version of the compiler, and would insert the same exploits into the new compiler. A review of the source code for the
login
command or the updated compiler would not reveal any malicious code.
This exploit was equivalent to a rootkit.
The first documented
computer virus
A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code. If this replication succeeds, the affected areas are then said to be "infected" with a compu ...
to target the
personal computer, discovered in 1986, used
cloaking
Cloaking is a search engine optimization (SEO) technique in which the content presented to the search engine spider is different from that presented to the user's browser. This is done by delivering content based on the IP addresses or the User ...
techniques to hide itself: the
Brain virus
Brain is the industry standard name for a computer virus that was released in its first form on 19 January 1986, and is considered to be the first computer virus for the IBM Personal Computer (IBM PC) and compatibles.
Description
Brain affect ...
intercepted attempts to read the
boot sector, and redirected these to elsewhere on the disk, where a copy of the original boot sector was kept.
Over time,
DOS-virus cloaking methods became more sophisticated. Advanced techniques included
hooking
In computer programming, the term hooking covers a range of techniques used to alter or augment the behaviour of an operating system, of applications, or of other software components by intercepting function calls or messages or events passe ...
low-level disk
INT 13H BIOS
interrupt calls to hide unauthorized modifications to files.
The first malicious rootkit for the
Windows NT operating system appeared in 1999: a trojan called ''NTRootkit'' created by
Greg Hoglund
Michael Gregory Hoglund is an American author, researcher, and serial entrepreneur in the cyber security industry. He is the founder of several companies, including Cenzic, HBGary and Outlier Security. Hoglund contributed early research to the ...
.
It was followed by ''HackerDefender'' in 2003.
The first rootkit targeting
Mac OS X appeared in 2009, while the
Stuxnet
Stuxnet is a malicious computer worm first uncovered in 2010 and thought to have been in development since at least 2005. Stuxnet targets supervisory control and data acquisition (SCADA) systems and is believed to be responsible for causing subs ...
worm was the first to target
programmable logic controllers (PLC).
Sony BMG copy protection rootkit scandal
In 2005,
Sony BMG published
CDs with
copy protection
Copy protection, also known as content protection, copy prevention and copy restriction, describes measures to enforce copyright by preventing the reproduction of software, films, music, and other media.
Copy protection is most commonly found o ...
and
digital rights management
Digital rights management (DRM) is the management of legal access to digital content. Various tools or technological protection measures (TPM) such as access control technologies can restrict the use of proprietary hardware and copyrighted works ...
software called
Extended Copy Protection
Extended Copy Protection (XCP) is a software package developed by the British company First 4 Internet (which on 20 November 2006, changed its name to Fortium Technologies Ltd) and sold as a copy protection or digital rights management (DRM) schem ...
, created by software company First 4 Internet. The software included a music player but silently installed a rootkit which limited the user's ability to access the CD.
Software engineer
Mark Russinovich
Mark Eugene Russinovich (born December 22, 1966) is a Spanish-born American software engineer and author who serves as CTO of Microsoft Azure. He was a cofounder of software producers Winternals before it was acquired by Microsoft in 2006.
Ea ...
, who created the rootkit detection tool
RootkitRevealer
RootkitRevealer is a proprietary freeware tool for rootkit detection on Microsoft Windows by Bryce Cogswell and Mark Russinovich. It runs on Windows XP and Windows Server 2003 (32-bit-versions only). Its output lists Windows Registry and file sy ...
, discovered the rootkit on one of his computers.
The ensuing scandal raised the public's awareness of rootkits.
To cloak itself, the rootkit hid any file starting with "$sys$" from the user. Soon after Russinovich's report, malware appeared which took advantage of the existing rootkit on affected systems.
One
BBC #REDIRECT BBC
Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board exam. ...
analyst called it a "
public relations nightmare." Sony BMG released
patches to
uninstall
An uninstaller, also called a deinstaller, is a variety of utility software designed to remove other software or parts of it from a computer. It is the opposite of an installer. Uninstallers are useful primarily when software components are install ...
the rootkit, but it exposed users to an even more serious vulnerability.
The company eventually recalled the CDs. In the United States, a
class-action lawsuit
A class action, also known as a class-action lawsuit, class suit, or representative action, is a type of lawsuit where one of the parties is a group of people who are represented collectively by a member or members of that group. The class actio ...
was brought against Sony BMG.
Greek wiretapping case 2004–05
The
Greek wiretapping case 2004–05, also referred to as Greek Watergate, involved the illegal
telephone tapping of more than 100
mobile phones on the
Vodafone Greece
Vodafone Greece (officially known as Vodafone-Panafon Hellenic Telecommunications Company S.A) is the Greek subsidiary of Vodafone. In 2004 it was the leading mobile operator in Greece. Its headquarters are in Chalandri - one of the northern ...
network belonging mostly to members of the
Greek government and top-ranking civil servants. The taps began sometime near the beginning of August 2004 and were removed in March 2005 without discovering the identity of the perpetrators. The intruders installed a rootkit targeting Ericsson's
AXE telephone exchange
The AXE telephone exchange is a product line of circuit switched digital telephone exchanges manufactured by Ericsson, a Swedish telecom company. It was developed in 1974 by Ellemtel, a research and development subsidiary of Ericsson and Tele ...
. According to ''
IEEE Spectrum
''IEEE Spectrum'' is a magazine edited by the Institute of Electrical and Electronics Engineers.
The first issue of ''IEEE Spectrum'' was published in January 1964 as a successor to ''Electrical Engineering''. The magazine contains peer-reviewe ...
'', this was "the first time a rootkit has been observed on a special-purpose system, in this case an Ericsson telephone switch."
The rootkit was designed to patch the memory of the exchange while it was running, enable
wiretapping while disabling audit logs, patch the commands that list active processes and active data blocks, and modify the data block
checksum
A checksum is a small-sized block of data derived from another block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. By themselves, checksums are often used to verify data ...
verification command. A "backdoor" allowed an operator with
sysadmin status to deactivate the exchange's transaction log, alarms and access commands related to the surveillance capability.
The rootkit was discovered after the intruders installed a faulty update, which caused
SMS
Short Message/Messaging Service, commonly abbreviated as SMS, is a text messaging service component of most telephone, Internet and mobile device systems. It uses standardized communication protocols that let mobile devices exchange short text ...
texts to be undelivered, leading to an automated failure report being generated. Ericsson engineers were called in to investigate the fault and discovered the hidden data blocks containing the list of phone numbers being monitored, along with the rootkit and illicit monitoring software.
Uses
Modern rootkits do not elevate access,
but rather are used to make another software payload undetectable by adding stealth capabilities.
Most rootkits are classified as
malware, because the payloads they are bundled with are malicious. For example, a payload might covertly steal user
password
A password, sometimes called a passcode (for example in Apple devices), is secret data, typically a string of characters, usually used to confirm a user's identity. Traditionally, passwords were expected to be memorized, but the large number of ...
s,
credit card
A credit card is a payment card issued to users (cardholders) to enable the cardholder to pay a merchant for goods and services based on the cardholder's accrued debt (i.e., promise to the card issuer to pay them for the amounts plus the o ...
information, computing resources, or conduct other unauthorized activities. A small number of rootkits may be considered utility applications by their users: for example, a rootkit might cloak a
CD-ROM
A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both compute ...
-emulation driver, allowing
video game users to defeat
anti-piracy Anti-piracy may refer to:
* Anti-piracy, protection against copying of computer software.
* Piracy#Anti-piracy measures anti-piracy measures, measures to counter maritime pirates.
See also
* Pirate (disambiguation)
{{Disambiguation
...
measures that require insertion of the original installation media into a physical optical drive to verify that the software was legitimately purchased.
Rootkits and their payloads have many uses:
*Provide an attacker with full access via a
backdoor
A back door is a door in the rear of a building. Back door may also refer to:
Arts and media
* Back Door (jazz trio), a British group
* Porta dos Fundos (literally “Back Door” in Portuguese) Brazilian comedy YouTube channel.
* Works so tit ...
, permitting unauthorized access to, for example, steal or falsify documents. One of the ways to carry this out is to subvert the login mechanism, such as the /bin/login program on
Unix-like systems or
GINA on Windows. The replacement appears to function normally, but also accepts a secret login combination that allows an attacker direct access to the system with administrative privileges, bypassing standard
authentication
Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proving an assertion, such as the identity of a computer system user. In contrast with identification, the act of indicati ...
and
authorization
Authorization or authorisation (see spelling differences) is the function of specifying access rights/privileges to resources, which is related to general information security and computer security, and to access control in particular. More for ...
mechanisms.
*Conceal other
malware, notably password-stealing
key loggers and
computer virus
A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code. If this replication succeeds, the affected areas are then said to be "infected" with a compu ...
es.
*Appropriate the compromised machine as a
zombie computer
In computing, a zombie is a computer connected to the Internet that has been compromised by a hacker via a computer virus, computer worm, or trojan horse program and can be used to perform malicious tasks under the remote direction of the hac ...
for attacks on other computers. (The attack originates from the compromised system or network, instead of the attacker's system.) "Zombie" computers are typically members of large
botnet
A botnet is a group of Internet-connected devices, each of which runs one or more bots. Botnets can be used to perform Distributed Denial-of-Service (DDoS) attacks, steal data, send spam, and allow the attacker to access the device and its conn ...
s that can–amongst other things–launch
denial-of-service attack
In computing, a denial-of-service attack (DoS attack) is a cyber-attack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connect ...
s, distribute
e-mail spam
Spam may refer to:
* Spam (food), a canned pork meat product
* Spamming, unsolicited or undesired electronic messages
** Email spam, unsolicited, undesired, or illegal email messages
** Messaging spam, spam targeting users of instant messaging ( ...
, and conduct
click fraud
Click, Klick and Klik may refer to:
Airlines
* Click Airways, a UAE airline
* Clickair, a Spanish airline
* MexicanaClick, a Mexican airline
Art, entertainment, and media Fictional characters
* Klick (fictional species), an alien race in th ...
.
In some instances, rootkits provide desired functionality, and may be installed intentionally on behalf of the computer user:
*Detect attacks, for example, in a
honeypot.
*Enhance emulation software and security software.
Alcohol 120%
Alcohol 120% is a disk image emulator created by Alcohol Soft. It can create and mount disc images in the proprietary Media Descriptor File format. Images in this format consist of a pair of .mds and .mdf files. Alcohol 120% can also convert ima ...
and
Daemon Tools
DAEMON Tools is a virtual drive and optical disc authoring program for Microsoft Windows and Mac OS.
Overview
DAEMON tools was originally a successor of ''Generic SafeDisc emulator'' and incorporated all of its features. The program claims ...
are commercial examples of non-hostile rootkits used to defeat copy-protection mechanisms such as
SafeDisc and
SecuROM.
Kaspersky antivirus software also uses techniques resembling rootkits to protect itself from malicious actions. It loads its own
drivers to intercept system activity, and then prevents other processes from doing harm to itself. Its processes are not hidden, but cannot be terminated by standard methods.
*Anti-theft protection: Laptops may have BIOS-based rootkit software that will periodically report to a central authority, allowing the laptop to be monitored, disabled or wiped of information in the event that it is stolen.
*Bypassing
Microsoft Product Activation
Microsoft Product Activation is a DRM technology used by Microsoft Corporation in several of its computer software programs, most notably its Windows operating system and its Office productivity suite. The procedure enforces compliance with th ...
Types
There are at least 69 types of rootkit, ranging from those at the lowest level in firmware (with the highest privileges), through to the least privileged user-based variants that operate in
Ring 3. Hybrid combinations of these may occur spanning, for example, user mode and kernel mode.
User mode
User-mode rootkits run in
Ring 3, along with other applications as user, rather than low-level system processes.
They have a number of possible installation vectors to intercept and modify the standard behavior of application programming interfaces (APIs). Some inject a
dynamically linked library (such as a
.DLL file on Windows, or a .dylib file on
Mac OS X) into other processes, and are thereby able to execute inside any target process to spoof it; others with sufficient privileges simply overwrite the memory of a target application. Injection mechanisms include:
*Use of vendor-supplied application extensions. For example,
Windows Explorer
File Explorer, previously known as Windows Explorer, is a file manager application that is included with releases of the Microsoft Windows operating system from Windows 95 onwards. It provides a graphical user interface for accessing the file ...
has public interfaces that allow third parties to extend its functionality.
*Interception of
messages
A message is a discrete unit of communication intended by the source for consumption by some recipient or group of recipients. A message may be delivered by various means, including courier, telegraphy, carrier pigeon and electronic bus.
A ...
.
*
Debuggers.
*Exploitation of
security vulnerabilities
Vulnerabilities are flaws in a computer system that weaken the overall security of the device/system. Vulnerabilities can be weaknesses in either the hardware itself, or the software that runs on the hardware. Vulnerabilities can be exploited by ...
.
*Function
hooking
In computer programming, the term hooking covers a range of techniques used to alter or augment the behaviour of an operating system, of applications, or of other software components by intercepting function calls or messages or events passe ...
or patching of commonly used APIs, for example, to hide a running process or file that resides on a filesystem.
Kernel mode
Kernel-mode rootkits run with the highest operating system privileges (
Ring 0) by adding code or replacing portions of the core operating system, including both the
kernel
Kernel may refer to:
Computing
* Kernel (operating system), the central component of most operating systems
* Kernel (image processing), a matrix used for image convolution
* Compute kernel, in GPGPU programming
* Kernel method, in machine learni ...
and associated
device drivers. Most operating systems support kernel-mode device drivers, which execute with the same privileges as the operating system itself. As such, many kernel-mode rootkits are developed as device drivers or loadable modules, such as
loadable kernel modules in
Linux or
device drivers in
Microsoft Windows. This class of rootkit has unrestricted security access, but is more difficult to write.
The complexity makes bugs common, and any bugs in code operating at the kernel level may seriously impact system stability, leading to discovery of the rootkit.
One of the first widely known kernel rootkits was developed for
Windows NT 4.0
Windows NT 4.0 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It is the direct successor to Windows NT 3.51, which was released to manufacturing on July 31, 1996, and then to retail ...
and released in
Phrack magazine in 1999 by
Greg Hoglund
Michael Gregory Hoglund is an American author, researcher, and serial entrepreneur in the cyber security industry. He is the founder of several companies, including Cenzic, HBGary and Outlier Security. Hoglund contributed early research to the ...
. Kernel rootkits can be especially difficult to detect and remove because they operate at the same
security level as the operating system itself, and are thus able to intercept or subvert the most trusted operating system operations. Any software, such as
antivirus software
Antivirus software (abbreviated to AV software), also known as anti-malware, is a computer program used to prevent, detect, and remove malware.
Antivirus software was originally developed to detect and remove computer viruses, hence the nam ...
, running on the compromised system is equally vulnerable. In this situation, no part of the system can be trusted.
A rootkit can modify data structures in the Windows kernel using a method known as ''
direct kernel object manipulation'' (DKOM). This method can be used to hide processes. A kernel mode rootkit can also hook the
System Service Descriptor Table (SSDT), or modify the gates between user mode and kernel mode, in order to cloak itself.
Similarly for the
Linux operating system, a rootkit can modify the ''system call table'' to subvert kernel functionality. It is common that a rootkit creates a hidden, encrypted filesystem in which it can hide other malware or original copies of files it has infected. Operating systems are evolving to counter the threat of kernel-mode rootkits. For example, 64-bit editions of Microsoft Windows now implement mandatory signing of all kernel-level drivers in order to make it more difficult for untrusted code to execute with the highest privileges in a system.
Bootkits
A kernel-mode rootkit variant called a bootkit can infect startup code like the
Master Boot Record (MBR),
Volume Boot Record (VBR), or
boot sector, and in this way can be used to attack
full disk encryption systems.
An example of such an attack on disk encryption is the "
evil maid attack", in which an attacker installs a bootkit on an unattended computer. The envisioned scenario is a maid sneaking into the hotel room where the victims left their hardware. The bootkit replaces the legitimate
boot loader
A bootloader, also spelled as boot loader or called boot manager and bootstrap loader, is a computer program that is responsible for booting a computer.
When a computer is turned off, its softwareincluding operating systems, application code, an ...
with one under their control. Typically the malware loader persists through the transition to
protected mode
In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as virtual memory, paging and safe multi-tasking ...
when the kernel has loaded, and is thus able to subvert the kernel.
For example, the "Stoned Bootkit" subverts the system by using a compromised
boot loader
A bootloader, also spelled as boot loader or called boot manager and bootstrap loader, is a computer program that is responsible for booting a computer.
When a computer is turned off, its softwareincluding operating systems, application code, an ...
to intercept encryption keys and passwords. In 2010, the Alureon rootkit has successfully subverted the requirement for 64-bit kernel-mode driver signing in
Windows 7
Windows 7 is a major release of the Windows NT operating system developed by Microsoft. It was Software release life cycle#Release to manufacturing (RTM), released to manufacturing on July 22, 2009, and became generally available on October 22, ...
, by modifying the
master boot record. Although not malware in the sense of doing something the user doesn't want, certain "Vista Loader" or "Windows Loader" software work in a similar way by injecting an
ACPI
Advanced Configuration and Power Interface (ACPI) is an open standard that operating systems can use to discover and configure computer hardware components, to perform power management (e.g. putting unused hardware components to sleep), auto con ...
SLIC (System Licensed Internal Code) table in the RAM-cached version of the BIOS during boot, in order to defeat the
Windows Vista and Windows 7 activation process. This vector of attack was rendered useless in the (non-server) versions of
Windows 8, which use a unique, machine-specific key for each system, that can only be used by that one machine. Many antivirus companies provide free utilities and programs to remove bootkits.
Hypervisor level
Rootkits have been created as Type II
Hypervisor
A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called ...
s in academia as proofs of concept. By exploiting hardware virtualization features such as
Intel VT or
AMD-V
x86 virtualization is the use of hardware-assisted virtualization capabilities on an x86/x86-64 CPU.
In the late 1990s x86 virtualization was achieved by complex software techniques, necessary to compensate for the processor's lack of hardware-as ...
, this type of rootkit runs in Ring -1 and hosts the target operating system as a
virtual machine, thereby enabling the rootkit to intercept hardware calls made by the original operating system.
Unlike normal hypervisors, they do not have to load before the operating system, but can load into an operating system before promoting it into a virtual machine.
A hypervisor rootkit does not have to make any modifications to the kernel of the target to subvert it; however, that does not mean that it cannot be detected by the guest operating system. For example, timing differences may be detectable in
CPU
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...
instructions.
The "SubVirt" laboratory rootkit, developed jointly by
Microsoft and
University of Michigan researchers, is an academic example of a virtual-machine–based rootkit (VMBR),
while
Blue Pill software is another. In 2009, researchers from Microsoft and
North Carolina State University demonstrated a hypervisor-layer anti-rootkit called
Hooksafe, which provides generic protection against kernel-mode rootkits.
Windows 10 introduced a new feature called "Device Guard", that takes advantage of virtualization to provide independent external protection of an operating system against rootkit-type malware.
Firmware and hardware
A
firmware rootkit uses device or platform firmware to create a persistent malware image in hardware, such as a
router,
network card,
hard drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magneti ...
, or the system
BIOS
In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the b ...
.
The rootkit hides in firmware, because firmware is not usually inspected for
code integrity Code integrity is a measurement used in the software delivery lifecycle. It measures how high the source code's quality is when it is passed on to QA, and is affected by how thoroughly the code was processed by correctness-checking processes (wheth ...
. John Heasman demonstrated the viability of firmware rootkits in both
ACPI
Advanced Configuration and Power Interface (ACPI) is an open standard that operating systems can use to discover and configure computer hardware components, to perform power management (e.g. putting unused hardware components to sleep), auto con ...
firmware routines and in a
PCI expansion card
ROM
Rom, or ROM may refer to:
Biomechanics and medicine
* Risk of mortality, a medical classification to estimate the likelihood of death for a patient
* Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac
* R ...
. In October 2008, criminals tampered with European
credit-card
A credit card is a payment card issued to users (cardholders) to enable the cardholder to pay a merchant for goods and services based on the cardholder's accrued debt (i.e., promise to the card issuer to pay them for the amounts plus the oth ...
-reading machines before they were installed. The devices intercepted and transmitted credit card details via a mobile phone network. In March 2009, researchers Alfredo Ortega and
Anibal Sacco published details of a
BIOS
In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the b ...
-level Windows rootkit that was able to survive disk replacement and operating system re-installation. A few months later they learned that some laptops are sold with a legitimate rootkit, known as Absolute
CompuTrace or Absolute
LoJack for Laptops, preinstalled in many BIOS images. This is an anti-
theft technology system that researchers showed can be turned to malicious purposes.
Intel Active Management Technology
Intel Active Management Technology (AMT) is hardware and firmware for remote out-of-band management of select business computers, running on the Intel Management Engine, a microprocessor subsystem not exposed to the user, intended for monitorin ...
, part of
Intel vPro
Intel vPro technology is an umbrella marketing term used by Intel for a large collection of computer hardware technologies, including VT-x, VT-d, Trusted Execution Technology (TXT), and Intel Active Management Technology (AMT). When the vPro bra ...
, implements
out-of-band management, giving administrators
remote administration
Remote administration refers to any method of controlling a computer from a remote location. Software that allows remote administration is becoming increasingly common and is often used when it is difficult or impractical to be physically near a ...
,
remote management
Remote monitoring and management (RMM) is the process of supervising and controlling IT systems (such as network devices, desktops, servers and mobile devices) by means of locally installed agents that can be accessed by a management service pr ...
, and
remote control of PCs with no involvement of the host processor or BIOS, even when the system is powered off. Remote administration includes remote power-up and power-down, remote reset, redirected boot, console redirection, pre-boot access to BIOS settings, programmable filtering for inbound and outbound network traffic, agent presence checking, out-of-band policy-based alerting, access to system information, such as hardware asset information, persistent event logs, and other information that is stored in dedicated memory (not on the hard drive) where it is accessible even if the OS is down or the PC is powered off. Some of these functions require the deepest level of rootkit, a second non-removable spy computer built around the main computer. Sandy Bridge and future chipsets have "the ability to remotely kill and restore a lost or stolen PC via 3G". Hardware rootkits built into the
chipset
In a computer system, a chipset is a set of electronic components in one or more integrated circuits known as a "Data Flow Management System" that manages the data flow between the processor, memory and peripherals. It is usually found on the mo ...
can help recover stolen computers, remove data, or render them useless, but they also present privacy and security concerns of undetectable spying and redirection by management or hackers who might gain control.
Installation and cloaking
Rootkits employ a variety of techniques to gain control of a system; the type of rootkit influences the choice of attack vector. The most common technique leverages
security vulnerabilities
Vulnerabilities are flaws in a computer system that weaken the overall security of the device/system. Vulnerabilities can be weaknesses in either the hardware itself, or the software that runs on the hardware. Vulnerabilities can be exploited by ...
to achieve surreptitious
privilege escalation. Another approach is to use a
Trojan horse, deceiving a computer user into trusting the rootkit's installation program as benign—in this case,
social engineering convinces a user that the rootkit is beneficial.
The installation task is made easier if the
principle of least privilege
In information security, computer science, and other fields, the principle of least privilege (PoLP), also known as the principle of minimal privilege (PoMP) or the principle of least authority (PoLA), requires that in a particular abstraction la ...
is not applied, since the rootkit then does not have to explicitly request elevated (administrator-level) privileges. Other classes of rootkits can be installed only by someone with physical access to the target system. Some rootkits may also be installed intentionally by the owner of the system or somebody authorized by the owner, e.g. for the purpose of
employee monitoring
Employee monitoring is the (often automated) surveillance of workers' activity. Organizations engage in employee monitoring for different reasons such as to track performance, to avoid legal liability, to protect trade secrets, and to address othe ...
, rendering such subversive techniques unnecessary. Some malicious rootkit installations are commercially driven, with a pay-per-install (PPI) compensation method typical for distribution.
Once installed, a rootkit takes active measures to obscure its presence within the host system through subversion or evasion of standard operating system
security
Security is protection from, or resilience against, potential harm (or other unwanted coercive change) caused by others, by restraining the freedom of others to act. Beneficiaries (technically referents) of security may be of persons and social ...
tools and
application programming interface
An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how t ...
(APIs) used for diagnosis, scanning, and monitoring. Rootkits achieve this by modifying the behavior of
core parts of an operating system through loading code into other processes, the installation or modification of
drivers, or
kernel modules. Obfuscation techniques include concealing running processes from system-monitoring mechanisms and hiding system files and other configuration data. It is not uncommon for a rootkit to disable the
event logging capacity of an operating system, in an attempt to hide evidence of an attack. Rootkits can, in theory, subvert ''any'' operating system activities.
The "perfect rootkit" can be thought of as similar to a "
perfect crime
Perfect crimes are crimes that are undetected, unattributed to an identifiable perpetrator, or otherwise unsolved or unsolvable as a kind of technical achievement on the part of the perpetrator. The term is used colloquially in law and fiction (e ...
": one that nobody realizes has taken place. Rootkits also take a number of measures to ensure their survival against detection and "cleaning" by antivirus software in addition to commonly installing into Ring 0 (kernel-mode), where they have complete access to a system. These include
polymorphism (changing so their "signature" is hard to detect), stealth techniques, regeneration, disabling or turning off anti-malware software,
and not installing on
virtual machines where it may be easier for researchers to discover and analyze them.
Detection
The fundamental problem with rootkit detection is that if the operating system has been subverted, particularly by a kernel-level rootkit, it cannot be trusted to find unauthorized modifications to itself or its components.
Actions such as requesting a list of running processes, or a list of files in a directory, cannot be trusted to behave as expected. In other words, rootkit detectors that work while running on infected systems are only effective against rootkits that have some defect in their camouflage, or that run with lower user-mode privileges than the detection software in the kernel.
As with
computer virus
A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code. If this replication succeeds, the affected areas are then said to be "infected" with a compu ...
es, the detection and elimination of rootkits is an ongoing struggle between both sides of this conflict.
Detection can take a number of different approaches, including looking for virus "signatures" (e.g. antivirus software), integrity checking (e.g.
digital signatures), difference-based detection (comparison of expected vs. actual results), and behavioral detection (e.g. monitoring CPU usage or network traffic).
For kernel-mode rootkits, detection is considerably more complex, requiring careful scrutiny of the System Call Table to look for
hooked functions where the malware may be subverting system behavior, as well as
forensic scanning of memory for patterns that indicate hidden processes. Unix rootkit detection offerings include Zeppoo,
chkrootkit,
rkhunter
rkhunter (Rootkit Hunter) is a Unix-based tool that scans for rootkits, backdoors and possible local exploits. It does this by comparing SHA-1 hashes of important files with ''known good'' ones in online databases, searching for default dire ...
and
OSSEC
OSSEC (Open Source HIDS SECurity) is a free, open-source host-based intrusion detection system (HIDS). It performs log analysis, integrity checking, Windows registry monitoring, rootkit detection, time-based alerting, and active response. It prov ...
. For Windows, detection tools include Microsoft Sysinternals
RootkitRevealer
RootkitRevealer is a proprietary freeware tool for rootkit detection on Microsoft Windows by Bryce Cogswell and Mark Russinovich. It runs on Windows XP and Windows Server 2003 (32-bit-versions only). Its output lists Windows Registry and file sy ...
,
Avast Antivirus
Avast Antivirus is a family of cross-platform internet security applications developed by Avast for Microsoft Windows, macOS, Android and iOS. The Avast Antivirus products include freeware and paid versions that provide computer security, brows ...
,
Sophos Anti-Rootkit,
F-Secure, Radix,
GMER, and
WindowsSCOPE
WindowsSCOPE is a memory forensics and reverse engineering product for Windows used for acquiring and analyzing volatile memory. One of its uses is in the detection and reverse engineering of rootkits and other malware. WindowsSCOPE supports acqu ...
. Any rootkit detectors that prove effective ultimately contribute to their own ineffectiveness, as malware authors adapt and test their code to escape detection by well-used tools.
[The process name of Sysinternals RootkitRevealer was targeted by malware; in an attempt to counter this countermeasure, the tool now uses a randomly generated process name.] Detection by examining storage while the suspect operating system is not operational can miss rootkits not recognised by the checking software, as the rootkit is not active and suspicious behavior is suppressed; conventional anti-malware software running with the rootkit operational may fail if the rootkit hides itself effectively.
Alternative trusted medium
The best and most reliable method for operating-system-level rootkit detection is to shut down the computer suspected of infection, and then to check its
storage by
booting
In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so some ...
from an alternative trusted medium (e.g. a "rescue"
CD-ROM
A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both compute ...
or
USB flash drive
A USB flash drive (also called a thumb drive) is a data storage device that includes flash memory with an integrated USB interface. It is typically removable, rewritable and much smaller than an optical disc. Most weigh less than . Since first ...
). The technique is effective because a rootkit cannot actively hide its presence if it is not running.
Behavioral-based
The behavioral-based approach to detecting rootkits attempts to infer the presence of a rootkit by looking for rootkit-like behavior. For example, by
profiling a system, differences in the timing and frequency of API calls or in overall CPU utilization can be attributed to a rootkit. The method is complex and is hampered by a high incidence of
false positives. Defective rootkits can sometimes introduce very obvious changes to a system: the
Alureon rootkit crashed Windows systems after a security update exposed a design flaw in its code. Logs from a
packet analyzer,
firewall
Firewall may refer to:
* Firewall (computing), a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts
* Firewall (construction), a barrier inside a building, designed to limit the spre ...
, or
intrusion prevention system
An intrusion detection system (IDS; also intrusion prevention system or IPS) is a device or software application that monitors a network or systems for malicious activity or policy violations. Any intrusion activity or violation is typically rep ...
may present evidence of rootkit behaviour in a networked environment.
Signature-based
Antivirus products rarely catch all viruses in public tests (depending on what is used and to what extent), even though security software vendors incorporate rootkit detection into their products. Should a rootkit attempt to hide during an antivirus scan, a stealth detector may notice; if the rootkit attempts to temporarily unload itself from the system, signature detection (or "fingerprinting") can still find it. This combined approach forces attackers to implement counterattack mechanisms, or "retro" routines, that attempt to terminate antivirus programs. Signature-based detection methods can be effective against well-published rootkits, but less so against specially crafted, custom-root rootkits.
Difference-based
Another method that can detect rootkits compares "trusted" raw data with "tainted" content returned by an
API
An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...
. For example,
binaries
A binary file is a computer file that is not a text file. The term "binary file" is often used as a term meaning "non-text file". Many binary file formats contain parts that can be interpreted as text; for example, some computer document fil ...
present on disk can be compared with their copies within
operating memory (in some operating systems, the in-memory image should be identical to the on-disk image), or the results returned from
file system or
Windows Registry
The Windows Registry is a hierarchical database that stores low-level settings for the Microsoft Windows operating system and for applications that opt to use the registry. The kernel, device drivers, services, Security Accounts Manager, and u ...
APIs can be checked against raw structures on the underlying physical disks
—however, in the case of the former, some valid differences can be introduced by operating system mechanisms like memory relocation or
shimming. A rootkit may detect the presence of such a difference-based scanner or
virtual machine (the latter being commonly used to perform forensic analysis), and adjust its behaviour so that no differences can be detected. Difference-based detection was used by
Russinovich's ''RootkitRevealer'' tool to find the Sony DRM rootkit.
Integrity checking
Code signing
Code signing is the process of digitally signing executables and scripts to confirm the software author and guarantee that the code has not been altered or corrupted since it was signed. The process employs the use of a cryptographic hash to v ...
uses
public-key infrastructure to check if a file has been modified since being
digitally signed
A digital signature is a mathematical scheme for verifying the authenticity of digital messages or documents. A valid digital signature, where the prerequisites are satisfied, gives a recipient very high confidence that the message was created b ...
by its publisher. Alternatively, a system owner or administrator can use a
cryptographic hash function
A cryptographic hash function (CHF) is a hash algorithm (a map of an arbitrary binary string to a binary string with fixed size of n bits) that has special properties desirable for cryptography:
* the probability of a particular n-bit output re ...
to compute a "fingerprint" at installation time that can help to detect subsequent unauthorized changes to on-disk code libraries. However, unsophisticated schemes check only whether the code has been modified since installation time; subversion prior to that time is not detectable. The fingerprint must be re-established each time changes are made to the system: for example, after installing security updates or a
service pack. The hash function creates a ''message digest'', a relatively short code calculated from each bit in the file using an algorithm that creates large changes in the message digest with even smaller changes to the original file. By recalculating and comparing the message digest of the installed files at regular intervals against a trusted list of message digests, changes in the system can be detected and monitored—as long as the original baseline was created before the malware was added.
More-sophisticated rootkits are able to subvert the verification process by presenting an unmodified copy of the file for inspection, or by making code modifications only in memory, reconfiguration registers, which are later compared to a white list of expected values. The code that performs hash, compare, or extend operations must also be protected—in this context, the notion of an ''immutable root-of-trust'' holds that the very first code to measure security properties of a system must itself be trusted to ensure that a rootkit or bootkit does not compromise the system at its most fundamental level.
Memory dumps
Forcing a complete dump of
virtual memory
In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very l ...
will capture an active rootkit (or a
kernel dump in the case of a kernel-mode rootkit), allowing offline
forensic analysis
Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal p ...
to be performed with a
debugger against the resulting
dump file
In computing, a core dump, memory dump, crash dump, storage dump, system dump, or ABEND dump consists of the recorded state of the working memory of a computer program at a specific time, generally when the program has crashed or otherwise termina ...
, without the rootkit being able to take any measures to cloak itself. This technique is highly specialized, and may require access to non-public
source code or
debugging symbols. Memory dumps initiated by the operating system cannot always be used to detect a hypervisor-based rootkit, which is able to intercept and subvert the lowest-level attempts to read memory
—a hardware device, such as one that implements a
non-maskable interrupt, may be required to dump memory in this scenario.
Virtual machines also make it easier to analyze the memory of a compromised machine from the underlying hypervisor, so some rootkits will avoid infecting virtual machines for this reason.
Removal
Manual removal of a rootkit is often extremely difficult for a typical computer user,
but a number of security-software vendors offer tools to automatically detect and remove some rootkits, typically as part of an
antivirus suite. , Microsoft's monthly
Windows Malicious Software Removal Tool
__NOTOC__
Microsoft Windows Malicious Software Removal Tool is a freely distributed virus removal tool developed by Microsoft for the Microsoft Windows operating system. First released on January 13, 2005, it is an on-demand anti-virus tool ("on ...
is able to detect and remove some classes of rootkits. Also, Windows Defender Offline can remove rootkits, as it runs from a trusted environment before the operating system starts. Some antivirus scanners can bypass
file system APIs, which are vulnerable to manipulation by a rootkit. Instead, they access raw file system structures directly, and use this information to validate the results from the system APIs to identify any differences that may be caused by a rootkit.
[In theory, a sufficiently sophisticated kernel-level rootkit could subvert read operations against raw file system data structures as well, so that they match the results returned by APIs.] There are experts who believe that the only reliable way to remove them is to re-install the operating system from trusted media.
This is because antivirus and malware removal tools running on an untrusted system may be ineffective against well-written kernel-mode rootkits. Booting an alternative operating system from trusted media can allow an infected system volume to be mounted and potentially safely cleaned and critical data to be copied off—or, alternatively, a forensic examination performed.
Lightweight operating systems such as
Windows PE,
Windows Recovery Console
The Recovery Console is a feature of the Windows 2000, Windows XP and Windows Server 2003 operating systems. It provides the means for administrators to perform a limited range of tasks using a command-line interface.
Its primary function is to ...
,
Windows Recovery Environment
Windows Preinstallation Environment (also known as Windows PE and WinPE) is a lightweight version of Windows used for the deployment of PCs, workstations, and servers, or troubleshooting an operating system while it is offline. It is intended ...
,
BartPE
BartPE (Bart's Preinstalled Environment) is a discontinued tool that customizes Windows XP or Windows Server 2003 into a lightweight environment, similar to Windows Preinstallation Environment, which could be run from a Live CD or Live USB drive. ...
, or
Live Distros can be used for this purpose, allowing the system to be "cleaned". Even if the type and nature of a rootkit is known, manual repair may be impractical, while re-installing the operating system and applications is safer, simpler and quicker.
Defenses
System
hardening represents one of the first layers of defence against a rootkit, to prevent it from being able to install. Applying
security patches, implementing the
principle of least privilege
In information security, computer science, and other fields, the principle of least privilege (PoLP), also known as the principle of minimal privilege (PoMP) or the principle of least authority (PoLA), requires that in a particular abstraction la ...
, reducing the
attack surface
The attack surface of a software environment is the sum of the different points (for " attack vectors") where an unauthorized user (the "attacker") can try to enter data to or extract data from an environment. Keeping the attack surface as small a ...
and installing antivirus software are some standard security best practices that are effective against all classes of malware.
New secure boot specifications like
UEFI
UEFI (Unified Extensible Firmware Interface) is a set of specifications written by the UEFI Forum. They define the architecture of the platform firmware used for booting and its interface for interaction with the operating system. Examples ...
have been designed to address the threat of bootkits, but even these are vulnerable if the security features they offer are not utilized.
For server systems, remote server attestation using technologies such as Intel
Trusted Execution Technology (TXT) provide a way of verifying that servers remain in a known good state. For example,
Microsoft Bitlocker
BitLocker is a full volume encryption feature included with Microsoft Windows versions starting with Windows Vista. It is designed to protect data by providing encryption for entire volumes. By default, it uses the AES encryption algorithm in ...
's encryption of data-at-rest verifies that servers are in a known "good state" on bootup.
PrivateCore
PrivateCore is a venture-backed startup located in Palo Alto, California that develops software to secure server data through server attestation and memory encryption. The company's attestation and memory encryption technology fills a gap that e ...
vCage is a software offering that secures data-in-use (memory) to avoid bootkits and rootkits by verifying servers are in a known "good" state on bootup. The PrivateCore implementation works in concert with Intel TXT and locks down server system interfaces to avoid potential bootkits and rootkits.
See also
*
Computer security conference
A computer security conference is a convention for individuals involved in computer security. They generally serve as meeting places for system and network administrators, hackers, and computer security experts.
Events
Common activities at hacke ...
*
Host-based intrusion detection system
A host-based intrusion detection system (HIDS) is an intrusion detection system that is capable of monitoring and analyzing the internals of a computing system as well as the network packets on its network interfaces, similar to the way a netwo ...
*
Man-in-the-middle attack
*''
The Rootkit Arsenal: Escape and Evasion in the Dark Corners of the System''
Notes
References
Further reading
*
*
*
*
*
External links
*
{{Authority control
Types of malware
Privilege escalation exploits
Cryptographic attacks
Cyberwarfare