What is a trojan horse and what threat does it pose?

Since "Trojan Horses" (or Backdoors) have been in the news just recently, the term probably sounds familiar to you. But perhaps you're not quite sure what a Trojan Horse is and what damage it is capable of doing to your system. Trojan Horses, of which there are now more than one thousand in circulation (including modifications and variants), are a relatively new and probably the most dangerous strain of viruses that have appeared in recent times. They also threaten to overwhelm systems that only run anti-virus applications and firewalls as a means of combating the threat.

Today's Trojans as they are commonly referred to as, have now attained such a degree of sophistication that they pose a real threat to any user who hasn't taken adequate precautions to protect their data.

The name "Trojan Horse" derives itself from a page in Greek history when the Greeks had lain siege to the fortified city of Troy for over ten years. Their spy, a Greek called Sinon offered the Trojans a gift in the form of a wooden horse and convinced them that by accepting it, they would become invincible. The horse though was hollow and was occupied by a contingent of Greek soldiers. When they emerged in the dead of night and opened the city gates, the Greeks swarmed in, slaughtered its citizens and subsequently pillaged, burned and laid waste to the city. In the IT environment, the Trojan Horse acts as a means of entering the victim's computer undetected and then allowing a remote user unrestricted access to any data stored on the user's hard disk drive whenever he or she goes online. In this way, the user gets burned and like the unfortunate citizens of Troy, may only discover that fact when it is too late.

These types of viruses were originally designed as a means of self expression by gifted programmers and did little more than to cause the system to lock up, behave abnormally in a specific way or perhaps cause loss of data on the user's machine.

TEXT 3

Increase your knowledge of computer viruses

What is a virus?

In 1983, researcher Fred Cohen defined a computer virus as “a program that can “infect” other programs by modifying them to include a version of itself.” This means that viruses copy themselves, usually by encryption* or by mutating** slightly each time they copy. There are several types of viruses, but the ones that are the most dangerous are designed to corrupt your computer or software programs. Viruses can range from an irritating*** message flashing on your computer screen to eliminating data on your hard drive. Viruses often use your computer's internal clock as a trigger. Some of the most popular dates used are Friday the 13th and famous birthdays. It is important to remember that viruses are dangerous only if you execute (start) an infected program. There are three main kinds of viruses. Each kind is based on the way the virus spreads.

1. Boot Sector Viruses - These viruses attach themselves to floppy disks and then copy themselves into the boot sector of your hard drive. (The boot sector is the set of instructions your computer uses when it starts up.) When you start your computer (or reboot it; your hard drive gets infected. You can get boot sector viruses only from an infected floppy disk. You cannot get one from sharing files or executing programs. This type of virus is becoming less common because today's computers do not require a boot disk to start, but they can still be found on disks that contain other types of files.

One of the most common boot sector viruses is called "Monkey”, also known as "Stoned".

2. Program Viruses - These viruses (also known as traditional file viruses) attach themselves to programs' executable files. They can infect any file that your computer 113 runs when it launches a program. When you start a program that contains a virus, the virus usually loads into your computer's memory. When the virus is in your computer's memory, it can infect any other program that is started. Program viruses that have circulated recently are "SKA" and "Loveletter." 3. Macro Viruses - These viruses attach themselves to templates that are used to create documents or spreadsheets. Once a template is infected, every document or spreadsheet you open using that program also will become infected. Macro viruses are widespread because they infect commonly used office applications and spread between PCs and Macintoshes. Macro viruses include “Concept”, “Melissa”, and “Have a Nice Day”.

Notes:

*encryption - кодирование

**mutating - мутация

***irritating – раздражающий

Exercise 1. Say what you have learned about:

a) boot sector viruses

b) program viruses

c) macro viruses

Exercise 2. Compare this subdivision with the subdivision of viruses in the main text.

TEXT 4

Read the text and answer the questions asked in the text.