Types of Computer viruses

A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or the Internet, or by carrying it on a removable medium such as a floppy disk, CD, or USB drive. Additionally, viruses can spread to other computers by infecting files on a network file system or a file system that is accessed by another computer.

Most personal computers are now connected to the Internet, facilitating the spread of malicious code. Today's viruses may also take advantage of network services such as the World Wide Web, e-mail to spread.

Some viruses are programmed to damage the computer by damaging programs, deleting files, or reformatting the hard disk. Others are not designed to do any damage, but simply replicate themselves and perhaps make their presence known by presenting text, video, or audio messages. Even these benign viruses can create problems for the computer user. They typically take up computer memory used by legitimate programs. As a result, they often cause erratic behavior and can result in data loss and system crashes.

The Creeper virus was first detected on ARPANET, the forerunner of the Internet in the early 1970s. It propagated via the TENEX operating system. It would display the message "I'M THE CREEPER: CATCH ME IF YOU CAN.". It is rumored that the Reaper program, which appeared shortly after and sought out copies of the Creeper and deleted them, may have been written by the creator of the Creeper in a fit of regret.

Before computer networks became widespread, most viruses spread on removable media, particularly floppy disks. In the early days of the personal computer, many users regularly exchanged information and programs on floppies.

Traditional computer viruses emerged in the 1980s. Since the mid-1990s, macro viruses have become common. Most of these viruses are written in the scripting languages for Microsoft programs such as Word and Excel. Since Word and Excel were also available for Mac OS, most of these viruses were able to spread on Macintosh computers as well.

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.

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. Many viruses attack their host systems on specific dates, such as Friday the 13th or April Fool's Day. Trojans that activate on certain dates are often called "time bombs".

The most common activator for a logic bomb is a date. The logic bomb checks the system date and does nothing until a pre-programmed date and time is reached. At that point, the logic bomb activates and executes its code.

A logic bomb could also be programmed to wait for a certain message from the programmer.

A logic bomb can also be programmed to activate on a wide variety of other variables, such as when a database grows past a certain size or a users home directory is deleted.

The most dangerous form of the logic bomb is a logic bomb that activates when something doesn't happen.

Because a logic bomb does not replicate itself, it is very easy to write a logic bomb program. This also means that a logic bomb will not spread to unintended victims. In some ways, a logic bomb is the most civilized programmed threat, because a logic bomb must be targeted against a specific victim.

The classic use for a logic bomb is to ensure payment for software. If payment is not made by a certain date, the logic bomb activates and the software automatically deletes itself. A more malicious form of that logic bomb would also delete other data on the system.

Computer worm

A computer worm is a self-replicating computer program. It uses a network to send copies of itself to other nodes and it may do so without any user intervention. Unlike a virus, it does not need to attach itself to an existing program.

Protecting against dangerous computer worms

Worms spread by exploiting vulnerabilities in operating systems. All vendors supply regular security updates, and if these are installed to a machine then the majority of worms are unable to spread to it.

Users need to be wary of opening unexpected email, and should not run attached files or programs, or visit web sites that are linked to such emails.

Anti-virus and anti-spyware software are helpful, but must be kept up-to-date with new pattern files at least every few days. The use of a firewall is also recommended.

4. Match column A with column B

A	B
1. to be accessed by	a. сменное съёмное средство
2. to become widespread	b. продвигать
3. to exploit vulnerability	с. приводить к…
4. erratic behavior	d. получить широкое распространение
5. be targeted against	e. ошибочное, неуправляемое поведение
6. to take advantage of	f. инициировать и исполнять код
7. to activate and execute one’s code	g. перехитрить кого-либо/что-либо
8. to facilitate	h. (вос)пользоваться уязвимостью
9. removable medium	i. получить доступ
10. to result in	j. быть нацеленным против

5. Comment on the following:

CD, USR, ARPANET, TENEX, 1970s, 1980s, 1990s, 13

6. Give summary of the text

Unit 5. Viruses multiply like rabbits

1. Read the following words correctly and guess their meaning:

programmer, industrialized, epidemics, unique, destructive, professional, teenager, vandalism, political, company, cyber-espionage, publicity, client, special, laboratories, specialize, infrastructure, organization, department, security, agency

2. Read and translate the following word combinations:

destructive program, unique ability, political reason, computer network, virus creator, viral epidemics, virus attacks, Security Institute, insurance company, debugged program, competitive purpose, unauthorized sources, to avoid publicity, special services, rival state

3. Read the text trying to find verbs connected with the sphere of writing and fighting viruses (e.g. to write viruses, …)

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