How Computer virus work? and How To Protect from these Viruses ? Posted by Stranger on 6:13 AM Digg it Bookmark it Stumble it Email to friend

A computer virus is a computer program that can copy itself and infect a computerwithout the permission or knowledge of the
owner. The term "virus" is also commonly but erroneously used to refer to other types of malware, adware, and spyware programs
that do not have the reproductive ability. A true virus can only spread from one computer to another (in some form of executable
code) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or
carried it on a removable medium such as a floppy disk, CD, DVD, or USB drive.Viruses can increase their chances of spreading to
other computers by infecting files on a network file system or a file system that is accessed by another computer. Viruses

A virus is a small piece of software that piggybacks on real programs. For example, a virus might attach itself to a program such as a spreadsheet program. Each time thespreadsheet program runs, the virus runs, too, and it has the chance to reproduce (by attaching to other programs) or wreak havoc.

E-Mail Viruses

An E-Mail virus could be a form of a macro virus that spreds itself to all the contact located in the hosts email address book, If any of the e-mail recipients open the attachment of the infected mail, It spreads to the new host's address book contacts, and then proceeds to send itself to all those contacts as well. These days, e-mail viruses van infect host even if the infected e-mail is previewed in a mail client. One of the most common and destructive e-mail viruses is the ILOVEYOU virus.

Boot Sector Viruses

A boot sector virus affects the boot sector of a hard disk, which is a very crucial part. The boot sector is where all information about the drive is stored, along with a program that makes it possible for the operating systems to boot up. By inserting its code into the boot sector, a virus guarantees that it loads into memory during every boot sequence.

A boot virus does not affect files; instead, it affects the disks that contain them. Perhaps this is the reason for their downfall. During the days when programs were carried around on floppies, the boot sector viruses used to spread like wildfire. However, with the CD-ROM revolution, it became impossible to infect per-written data on a CD, which eventually stopped such viruses from spreading.

Though boot viruses still exist, they are rare compared to new age malicious software. Another reason why they're not so prevalent is that operating systems today protect the boot sector, which makes it difficult for them to thrive.

Worms

A worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole. It copies itself to the new machine using the security hole, and then starts replicating from there, as well.

How protect from these viruses ?

You can protect yourself against viruses with a few simple steps:

* If you are truly worried about traditional (as opposed to e-mail) viruses, you should be running a more secure operating system like UNIX. You never hear about viruses on these operating systems because the security features keep viruses (and unwanted human visitors) away from your hard disk.

* If you are using an unsecured operating system, then buying virus protection software is a nice safeguard.

* If you simply avoid programs from unknown sources (like the Internet), and instead stick with commercial software purchased on CDs, you eliminate almost all of the risk from traditional viruses. In addition, you should disable floppy disk booting -- most computers now allow you to do this, and that will eliminate the risk of a boot sector virus coming in from a floppy disk accidentally left in the drive.

* You should make sure that Macro Virus Protection is enabled in all Microsoft applications, and you should NEVER run macros in a document unless you know what they do. There is seldom a good reason to add macros to a document, so avoiding all macros is a great policy