О. В. Фёдорова е. В. Мезина е. В. Хамис английский язык в сфере информационных технологий и коммуникаций учебное пособие

The word “virus” is used in the same sense as the biological equivalent to describe all kinds of malware (malicious software), including worms or Trojans. A computer virus is a computer program written to alter the way a computer operates, without the permission or knowledge of the user. A true virus must replicate itself, and must execute itself. A computer virus will pass from one computer to another like a real biological virus passes from person to person. For example, it is estimated by experts that the Mydoom worm infected a quarter-million computers in a single day in January 2004. There are tens of thousands of viruses out there, and new ones are discovered every day. Here is the classification of basic types of viruses.

Viruses can be subdivided into a number of types, the main ones being: Boot sector viruses, Companion viruses, Email viruses, Logic bombs and time bombs, Macro viruses.

Two other types of malware are often classified as viruses, but are actually forms of distributing malware: Trojan horses and Worms.

A boot sector virus affects the boot sector of a hard disk, which is a very crucial part. The boot sector is where all information about the drive is stored, along with a program that makes it possible for the operating system to boot up. By inserting its code into the boot sector, a virus guarantees that it loads into memory during every boot sequence. A boot virus does not affect files; instead, it affects the disks that contain them. During the days when programs were carried around on floppies, the boot sector viruses used to spread like wildfire. However, with the CD-ROM revolution, it became impossible to infect pre-written data on a CD, which eventually stopped such viruses from spreading. Examples of boot viruses are Polyboot.B and AntiEXE.

Multipartite viruses are a combination of boot sector viruses and file viruses. These viruses come in through infected media and reside in memory. They then move on to the boot sector of the hard drive. From there, the virus infects executable files on the hard drive and spreads across the system. There aren’t too many multipartite viruses in existence today, but in their heyday, they accounted for some major problems due to their capacity to combine different infection techniques. A significantly famous multipartite virus is Ywinz.

A logic bomb employs code that lies inert until specific conditions are met. The resolution of the conditions will trigger a certain function (such as printing a message to the user and/or deleting files). Logic bombs may reside within standalone programs, or they may be part of worms or viruses. An example of a logic bomb would be a virus that waits to execute until it has infected a certain number of hosts. A time bomb is a subset of logic bomb, which is set to trigger on a particular date and/or time. An example of a time bomb is the infamous ‘Friday the 13th’ virus.

Macro Viruses infect files that are created using certain applications or programs that contain macros. These include Microsoft Office documents such as Word documents, Excel spreadsheets, PowerPoint presentations, Access databases, and other similar application files such as Corel Draw, AmiPro, etc. Since macro viruses are written in the language of the application, and not in that of the operating system, they are known to be platform-independent—they can spread between Windows, Mac, and any other system, so long as they’re running the required application. With the ever-increasing capabilities of macro languages in applications, and the possibility of infections spreading over net-works, these viruses are major threats. The first macro virus was written for Microsoft Word and was discovered back in August 1995. Today, there are thousands of macro viruses in existence—some examples are Relax, Melissa.A and Bablas.

The only function of Trojans is to destroy and delete files. They can automatically delete all the core system files on your machine. The Trojan could be controlled by the attacker or could be programmed to strike like logic bomb-starting on a specific day or at specific hour. Trojans are aimed to generate a lot of internet traffic on the victim’s machine, to the extent that the Internet connection is too overloaded to let the user visit a website or download anything. They infect as many machines as possible and simultaneously attack specific e-mail addresses with random subjects and contents that cannot be filtered.

Computer Worms are programs that reproduce and run independently, and travel across network connections. The main difference between viruses and worms is the method in which they reproduce and spread. A virus is dependent upon a host file or boot sector, and the transfer of files between machines to spread, while a worm can run completely independently and spread of its own accord through network connections. The security threat of worms is equivalent to that of a virus. Worms are capable of doing a whole range of damage such as destroying essential files in your system, slowing it down to a great extent, or even causing some essential programs to crash. Two famous examples of worms are the MS-Blaster and Sesser worms.