Computer Virus And Internet Worms Explained
Is your computer sluggish? It won’t open programs & you can’t get into anything? Well maybe you have a sick computer. Just as people get ill from viruses so do computers. When this happens you need to have a computer technician look at the computer to re-format & get rid of the virus. If you know something about computers you might be able to do this yourself.
What is Virus?
A virus is parasitic program written to intentionally enter a computer without the user’s permission or knowledge. The word parasitic is used because a virus attaches to files or boot sectors & replicates itself which allows it to spread. Though some viruses do little more than copy themselves others can cause serious damage or affect program & system performance. A virus should never be assumed harmless or left on a system.
Types of viruses
Viruses are classified by the ways they infect computer systems:
1 Program Executable program files such as those ending with the extensions .Com .Exe .Ovl .Drv .Sys .Bin
2 Boot Boot Record Master Boot FAT & Partition Table.
3 Multipartite Both program & boot infector.
What is Trojan Horse?
Besides being a large wooden horse used in the Trojan war 2500 years ago and more recently by Brad Pitt a Trojan Horse or Trojan is computer program that seems innocuous or harmless but conceals another more nasty function. Generally a Trojan is contained in a part of program brought into your computer from an outside source e.g. floppy disk CD internet download infected email . Trojans can be dangerous sometimes. For example a program may appear to be a computer game demo but while you enjoy the game it may be happily formatting your hard disk or emailing porn sites to everyone in your email address book.
Trojans are also used as a ‘back door’ or ‘trap door’ to sneak into a computer’s operating system’s information. An example is program that pretends to be the system log-in program such as you find in Windows NT/XP or Linux . When an unsuspecting user tries to log-in the Trojan program captures the user-name & password. Then it may indicate a failed log-in attempt & exit to the real log-in program. The user may successfully log into the system next time but by that time Trojan has also got enough details to log into the system.
Example Trojans
Notroj. This Trojan horse pretends to be a program that guards against Trojans. It’s actually a time bomb that wipes out the hard disk after it’s more than 70 percent full.
PWSteal.Refest A Trojan Horse that installs itself as a BHO Browser Helper Object for Internet Explorer & steals online banking information when it submitted in web forms.
PWSteal.Likmet.A A Trojan horse that displays a fake MSN Messenger logon window & steals the password provided.
Run.me. This is graphics program which plays the Star Spangled Banner & displays the American Flag while it worms its way into the hard disk & erases the data on it.
What is Worm?
A Worm is self-propagating program that works its way through a system or network like the Internet often causing damage. It does not require a host program to activate it. Someone has to insert a worm directly into network of interconnected computers where messages can be sent from one to another & data files & programs exchanged. An example is local area network where each computer has its own files programs operating systems & hard discs such as would be found in a university or corporate setting.
Example Worms
Alarm Clock Worm. A worm that reaches out through the network to an outgoing terminal one equipped with a modem & places wake-up calls to a list of users.
Worm Watcher. A special program which automatically takes steps to limit the size of a worm or shut it down it grows beyond a certain limit. The worm watcher also maintains a running log recording changes in the
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