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Fork Bomb
In computing, a fork bomb (also called rabbit virus) is a denial-of-service (DoS) attack wherein a process continually replicates itself to deplete available system resources, slowing down or crashing the system due to resource starvation. History Around 1978, an early variant of a fork bomb called wabbit was reported to run on a System/360 The IBM System/360 (S/360) is a family of mainframe computer systems announced by IBM on April 7, 1964, and delivered between 1965 and 1978. System/360 was the first family of computers designed to cover both commercial and scientific applicati .... It may have descended from a similar attack called RABBITS reported from 1969 on a Burroughs large systems, Burroughs 5500 at the University of Washington. Implementation Fork bombs operate both by consuming Central processing unit, CPU time in the process of Fork (system call), forking, and by saturating the operating system's process table. A basic implementation of a fork bomb is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Copy-on-write
Copy-on-write (COW), also called implicit sharing or shadowing, is a resource-management technique used in programming to manage shared data efficiently. Instead of copying data right away when multiple programs use it, the same data is shared between programs until one tries to modify it. If no changes are made, no private copy is created, saving resources. A copy is only made when needed, ensuring each program has its own version when modifications occur. This technique is commonly applied to memory, files, and data structures. In virtual memory management Copy-on-write finds its main use in operating systems, sharing the physical memory of computers running multiple processes, in the implementation of the fork() system call. Typically, the new process does not modify any memory and immediately executes a new process, replacing the address space entirely. It would waste processor time and memory to copy all of the old process's memory during the fork only to immediately dis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Logic Bomb
A logic bomb is a piece of code intentionally inserted into a software system that will set off a malicious function when specified conditions are met. For example, a programmer may hide a piece of code that starts deleting files (such as a salary database trigger), should they ever be terminated from the company. Software that is inherently malicious, such as viruses and worms, often contain logic bombs that execute a certain payload at a pre-defined time or when some other condition is met. This technique can be used by a virus or worm to gain momentum and spread before being noticed. Some viruses attack their host systems on specific dates, such as Friday the 13th or April Fools' Day. Trojans and other computer viruses that activate on certain dates are often called " time bombs". To be considered a logic bomb, the payload should be unwanted and unknown to the user of the software. As an example, trial programs with code that disables certain functionality after a set time ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deadlock (computer Science)
In concurrent computing, deadlock is any situation in which no member of some group of entities can proceed because each waits for another member, including itself, to take action, such as sending a message or, more commonly, releasing a lock. Deadlocks are a common problem in multiprocessing systems, parallel computing, and distributed systems, because in these contexts systems often use software or hardware locks to arbitrate shared resources and implement process synchronization. In an operating system, a deadlock occurs when a process or thread enters a waiting state because a requested system resource is held by another waiting process, which in turn is waiting for another resource held by another waiting process. If a process remains indefinitely unable to change its state because resources requested by it are being used by another process that itself is waiting, then the system is said to be in a deadlock. In a communications system, deadlocks occur mainly due to loss ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Billion Laughs Attack
In computer security, a billion laughs attack is a type of denial-of-service (DoS) attack which is aimed at parsers of XML documents. It is also referred to as an XML bomb or as an exponential entity expansion attack. Details The example attack consists of defining 10 entities, each defined as consisting of 10 of the previous entity, with the document consisting of a single instance of the largest entity, which expands to one billion copies of the first entity. Versions with larger amount of entries also exist. In the most frequently cited example, the first entity is the string " lol", hence the name "billion laughs". At the time this vulnerability was first reported, the computer memory used by a billion instances of the string "lol" would likely exceed that available to the process parsing the XML. While the original form of the attack was aimed specifically at XML parsers, the term may be applicable to similar subjects as well. The problem was first reported as early as 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zip Bomb
In computing, a zip bomb, also known as a decompression bomb or zip of death (ZOD), is a malicious archive file designed to crash or render useless the program or system reading it. The older the system or program, the less likely it is that the zip bomb will be detected. It is often employed to disable antivirus software, in order to create an opening for more traditional malware. A zip bomb allows a program to function normally, but, instead of hijacking the program's operation, it creates an archive that requires an excessive amount of time, disk space, computational power, or memory to unpack. Most modern antivirus programs can detect zip bombs and prevent the user from extracting anything from it. Details and use A zip bomb is usually a small file for ease of transport and to avoid suspicion. However, when the file is unpacked, its contents are more than the system can handle. A famous example of a zip bomb is titled ''42.zip'', which is a zip file of unknown authorship ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cgroups
cgroups (abbreviated from control groups) is a Linux kernel feature that limits, accounts for, and isolates the resource usage (CPU, memory, disk I/O, etc.) of a collection of processes. Engineers at Google started the work on this feature in 2006 under the name "process containers". In late 2007, the nomenclature changed to "control groups" to avoid confusion caused by multiple meanings of the term "container" in the Linux kernel context, and the control groups functionality was merged into the Linux kernel mainline in kernel version 2.6.24, which was released in January 2008. Since then, developers have added many new features and controllers, such as support for kernfs in 2014, firewalling, and unified hierarchy. cgroup v2 was merged in Linux kernel 4.5 with significant changes to the interface and internal functionality. Versions There are two versions of cgroups. Cgroups was originally written by Paul Menage and Rohit Seth, and merged into the mainline Linux ker ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pluggable Authentication Module
A pluggable authentication module (PAM) is a mechanism to integrate multiple low-level authentication schemes into a high-level application programming interface (API). PAM allows programs that rely on authentication to be written independently of the underlying authentication scheme. It was first proposed by Sun Microsystems in an Open Software Foundation Request for Comments (RFC) 86.0 dated October 1995. It was adopted as the authentication framework of the Common Desktop Environment. As a stand-alone open-source infrastructure, PAM first appeared in Red Hat Linux 3.0.4 in August 1996 in the Linux PAM project. PAM is currently supported in the AIX operating system, DragonFly BSD, FreeBSD, HP-UX, Linux, macOS, NetBSD and Solaris. Since no central standard of PAM behavior exists, there was a later attempt to standardize PAM as part of the X/Open UNIX standardization process, resulting in the X/Open Single Sign-on (XSSO) standard. This standard was not ratified, but the standar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GNU Bash
In computing, Bash (short for "''Bourne Again SHell''") is an interactive command interpreter and command programming language developed for UNIX-like operating systems. Created in 1989 by Brian Fox for the GNU Project, it is supported by the Free Software Foundation and designed as a 100% free alternative for the Bourne shell (sh) and other proprietary Unix shells. Since its inception, Bash has gained widespread adoption and is commonly used as the default login shell for numerous Linux distributions. It holds historical significance as one of the earliest programs ported to Linux by Linus Torvalds, alongside the GNU Compiler ( GCC). It is available on nearly all modern operating systems, making it a versatile tool in various computing environments. As a command-line interface (CLI), Bash operates within a terminal emulator, or text window, where users input commands to execute various tasks. It also supports the execution of commands from files, known as shell scripts, facil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alphanumericals
Alphanumericals or alphanumeric characters are any collection of number characters and letters in a certain language. Sometimes such characters may be mistaken one for the other. Merriam-Webster suggests that the term "alphanumeric" may often additionally refer to other symbols, such as punctuation and mathematical symbols. In the POSIX/C locale, there are either 36 (A–Z and 0–9, case insensitive) or 62 (A–Z, a–z and 0–9, case-sensitive) alphanumeric characters. Subsets of alphanumeric used in human interfaces When a string of mixed alphabets and numerals is presented for human interpretation, ambiguities arise. The most obvious is the similarity of the letters I, O and Q to the numbers 1 and 0. Therefore, depending on the application, various subsets of the alphanumeric were adopted to avoid misinterpretation by humans. In passenger aircraft, aircraft seat maps and seats were designated by row number followed by column letter. For wide bodied jets, the seats can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Job (Unix)
In Unix and Unix-like operating systems, job control refers to control of jobs by a shell, especially interactively, where a "job" is a shell's representation for a process group. Basic job control features are the suspending, resuming, or terminating of all processes in the job/process group; more advanced features can be performed by sending signals to the job. Job control is of particular interest in Unix due to its multiprocessing, and should be distinguished from job control generally, which is frequently applied to sequential execution (batch processing). Overview When using Unix or Unix-like operating systems via a terminal (or terminal emulator), a user will initially only have a single process running, their interactive shell (it may or may not be a login shell). Most tasks (directory listing, editing files, etc.) can easily be accomplished by letting the program take control of the terminal and returning control to the shell when the program exits – formally, by attac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pipeline (Unix)
In Unix-like computer operating systems, a pipeline is a mechanism for inter-process communication using message passing. A pipeline is a set of process (computing), processes chained together by their standard streams, so that the output text of each process (''stdout'') is passed directly as input (''stdin'') to the next one. The second process is started as the first process is still executing, and they are executed concurrency (computer science), concurrently. The concept of pipelines was championed by Douglas McIlroy at Unix's ancestral home of Bell Labs, during the development of Unix, shaping its Unix philosophy, toolbox philosophy. It is named by analogy to a physical pipeline transport, pipeline. A key feature of these pipelines is their "hiding of internals". This in turn allows for more clarity and simplicity in the system. The pipes in the pipeline are anonymous pipes (as opposed to named pipes), where data written by one process is buffered by the operating system un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
