Barrotes is a computer virus, considered as the first of Spanish origin, which appeared in December 1992, and was programmed in

assembly language In computing, assembly language (alternatively assembler language or symbolic machine code), often referred to simply as assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence bet ...

for DOS-based systems. Initially, although to a lesser extent, it was also called Toledo by the press, due to the location in the homonymous city of its first discovery, and registered as Virus:DOS/Barrotes by

Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...

. Like many viruses of the time, it remains dormant in the affected machine, waiting for a specific date to execute its malicious code, also called

payload Payload is the object or the entity that is being carried by an aircraft or launch vehicle. Sometimes payload also refers to the carrying capacity of an aircraft or launch vehicle, usually measured in terms of weight. Depending on the nature of t ...

, with the date chosen by its developer being 5 January, a very important date in Spain, as it is the night of the

Biblical Magi In Christianity, the Biblical Magi ( or ; singular: ), also known as the Three Wise Men, Three Kings, and Three Magi, are distinguished foreigners who visit Jesus after his birth, bearing gifts of gold, frankincense, and myrrh in homage to hi ...

, displaying the message ''«Virus BARROTES por OSoft»'' and the on-screen graphics of the characteristic bars that give it its name and make it look like the system is in a prison cell.

Features

The virus occupies a total of 1310

bytes The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable un ...

in size and infects

COM Com or COM may refer to: Computing * COM (hardware interface), a serial port interface on IBM PC-compatible computers * COM file, or .com file, short for "command", a file extension for an executable file in MS-DOS * .com, an Internet top-level ...

and

EXE Exe or EXE may refer to: * .exe, a file extension * exe., abbreviation for Executive (disambiguation)#Role, title, or function, executive Places * River Exe, in England * Exe Estuary, in England * Exe Island, in Exeter, England Transportation a ...

executable files. When an infected file is executed on the system, the malicious code of the virus is the first thing to execute, checking if it is already resident in memory, detecting if it has already been executed before, bypassing the infection process of the executed file, otherwise it proceeds to install itself in memory by registering the

interrupt vector An interrupt vector table (IVT) is a data structure that associates a list of interrupt handlers with a list of interrupt requests in a table of interrupt vectors. Each entry of the interrupt vector table, called an interrupt vector, is the addre ...

corresponding to

DOS DOS (, ) is a family of disk-based operating systems for IBM PC compatible computers. The DOS family primarily consists of IBM PC DOS and a rebranded version, Microsoft's MS-DOS, both of which were introduced in 1981. Later compatible syste ...

services ( int 21) in the virus header, thanks to which the virus will infect files on the system as the user executes them. It will then check if the date is 5 January to display the author's message and the bars, otherwise it runs the system normally, going unnoticed.

Propagation method

Barrotes has no automatic method of propagation beyond infecting local files on the machine affected by the virus. Its main method of dissemination, given the context of its time of action — the 90s— was the exchange of infected files via physical storage media, such as

floppy disks A floppy disk or floppy diskette (casually referred to as a floppy, a diskette, or a disk) is a type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined with a ...

Variants

Subsequently, new versions and variants of the virus appeared with more pronounced malicious effects, such as the Barrotes 1303 variant in 1996, which destroyed the

boot sector A boot sector is the disk sector, sector of a persistent data storage device (e.g., hard disk, floppy disk, optical disc, etc.) which contains machine code to be loaded into random-access memory (RAM) and then executed by a computer system's bui ...

of the hard disk, preventing the system from booting and accessing the information stored on it, changing the activation date to 23 September. Many computer systems were exposed to these effects.

References

Bibliography

* ''Pc Mania'', number 28, 1995 HOBBY PRESS, S.A.
Internet Archive
* ''OK PC'' number 17, 1993, New Publisher Press, S.A.
Internet Archive
* ''Virus Bulletin'', 1994, Network Security Management, UK, ISSN 0956-9979
Internet Archive

External links