Is your computer sluggish? It doesn’t open any programs and you can’t access anything? Well, maybe you have a sick computer. Just as people get sick from viruses, so do computers. In this case, a computer technician needs to examine the computer to reformat it and remove viruses. If you know anything about computers, you can probably do it yourself.
What are viruses?
Viruses are parasitic programs written to intentionally enter a computer without the user’s permission or knowledge. The word parasite is used because a virus attaches itself to a file or boot sector and replicates itself, allowing it to spread. While some viruses do little more than copy themselves, others can cause serious harm or hamper program and system performance. Viruses should not be rendered harmless or left on the system.
Viruses are classified according to how they infect computer systems:
1) Program: Executable program files such as those with the extension .Com, .Exe, .Ovl, .Drv, .Sys, .Bin
2) Boot: Boot Records, Master Boot, FAT and Partition Table.
3) Multipartite: program and boot infector.
What is a Trojan horse?
Aside from the massive wooden horse used in the Trojan Wars 2500 years ago (and more recently by Brad Pitt), a Trojan horse or trojan is a computer program that appears harmless or harmless but hides other, uglier features. Generally, a trojan is contained within a program that has been placed on your computer from an external source (e.g. floppy disk, CD, Internet download, infected e-mail). Trojans are sometimes dangerous. For example, a program might look like a computer game demo, but while you’re enjoying the game, it might happily format your hard drive or email porn sites to everyone in your email address book.
Trojans are also used as “back doors” or “trap doors” to sneak into computer operating system information. An example is a program pretending to be a system login program (like you would find on Windows NT/XP or Linux). When an unsuspecting user tries to log in, the Trojan horse program captures the username and password. A failed login attempt may then be displayed and the actual login program exited. The user may be able to successfully log into the system one more time, but by then the trojan has also obtained enough details to enter the system.
Nottroj. This Trojan horse pretends to be a program that protects against Trojans. It’s actually a ticking time bomb that wipes the hard drive once it’s more than 70 percent full.
PWSteal.Refest Trojan horse that installs itself as BHO (Browser Helper Object) for Internet Explorer and steals online banking information when submitted in web forms.
PWSteal.Likmet.A Trojan horse that displays a fake MSN Messenger login window and steals the provided password.
run… my. It is a graphics program that plays the Star Spangled Banner and displays the American flag when it infiltrates the hard drive and erases the data on it.
What are worms
Worms are self-propagating programs that work their way through a system or network (like the Internet), often causing damage. Does not require activation by the host program. Someone had to inject the worm directly into an interconnected network of computers where messages could be sent from one to another and data files and programs could be exchanged. An example is a local area network where each computer has its own files, operating system programs, and hard drives, such as might be found in a university or corporate environment.
Examples of worms
worm alarm clock. A worm that reaches outbound terminals (equipped with modems) over the network and wakes up a list of users.
worm watcher. A special program that automatically takes steps to limit the size of the worm or kill it grows beyond a certain threshold. Worm Watcher also maintains a change log record that runs