What is a virus?

A virus is a program that intentionally parasites to a computer without the user’s permission or knowledge. The word is a parasitic virus, because it is based on files or boot sectors and replicates that its spread. Although some viruses are not much more than copy themselves, others can cause serious damage or affect the performance of the system and program. A virus should never be assumed harmless and left in a system.

Types of Viruses

Viruses are, how they infect computer systems:

1) Program: Executable program files such as those ending with. COM,. Exe,. OVL,. Drv,. Sys. Bin
2) Boot: Boot Record, Master Boot, fat and partition table.
3) Multi: Both program and boot infector.

What is Trojan horse?

Apart from the fact that a large wooden horse in the Trojan war 2500 years ago (and more recently by Brad Pitt), a Trojan or Trojan Horse is a program that is harmless, or harmless, but there is another evil role. In general it is a trojan in a program in the computer from an external source – (eg diskette, CD, Internet download, e-mail infected). Trojans can sometimes be dangerous. For example, a program may be a demonstration of computer game, but enjoy the game, you’re welcome to format the hard disk or e-mail to all the porn sites in your address book, e-mail.

The Trojans are also known as a “backdoor” or “trap door” secretly in a computer operating system information. An example is a program that pretends to the system log-in program (as in Windows NT / XP or Linux). When a user tries to unsuspecting used to access the system, the Trojans captured the user name and password. Then, an error in the logon attempt, the reality and exit the program. The user can set the system the next time, but at this time also Trojan enough information to log into the system.

Example Trojans

Notroj. The Trojan horse, which is a protection against Trojans. It is actually a time bomb that will eliminate the hard drive for more than 70 percent complete.

PWSteal.Refest a Trojan horse is installed to ensure that a BHO (Browser Helper Object) for Internet Explorer and steals online banking information when you register in Web forms.

PWSteal.Likmet.AA Trojan horse that has a fake login window of MSN Messenger and steals the password.

Run.me. This is a graphics program, it plays the Star Spangled Banner and the American flag, while the worms its way into the hard drive and delete the data about them.

What is Worm?

A worm is a self-propagating program that pushes its way through a system or network (eg Internet), often cause damage. Is it not necessary, a host program to activate it. Someone has to create a worm into the network of interconnected computers that can send messages to each other and the information and exchange programs. An example is a local area network in which each team has its own files, programs and operating systems, such as hard disks are in a university or a corporate environment.

Example worms

Wake Worm. A worm that comes over the network to an output (one with a modem), and provides the test calls to a list of users.

Worm Watcher. A special program that automatically steps to limit the size of a worm, or turn it off, it grows over a certain limit. The worm also remain vigilant record changes in the registry