C omputer V irus is a computer progam that can copy itself and infect a computer without permission or knowledge of the user. The original may modify the copies or the copies may modify themselves, as occurs in a metamorphic virus. A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or carrying it on a removable medium such as a floppy disk, CD, USB drive or by the Internet. Additionally, viruses can spread to other computers by infecting files on a network file system or a file system that is accessed by another computer.
C omputer V irusES are small software programs that are designed to spread from one computer to another and to interfere with computer operation. A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.
Viruses are most easily spread by attachments in e-mail messages or instant messaging messages. That is why it is essential that you never open e-mail attachments unless you know who it's from and you are expecting it.Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files.Viruses also spread through downloads on the Internet. They can be hidden in illicit software or other files or programs you might download.
DESCRIPTION OF COMPUTER VIRUS
EXAMPLE OF VIRUSES
4k is a computer virus which infects COM files and EXE files.The virus was one of the first to employ Stealth tactics, infected systems will hang, displaying the message Frodo Lives, on the 22 September, which is also the date of birth Bilbo Baggins, a character from the Lord of the rings.This virus was spread without the aid of the Internet. It was ported between systems by floppy disks.
I LOVE U
The ILOVEYOU worm, also known as VBS/Loveletter and Love Bug worm , is a computer worm written in VBScript
The Melissa worm , also known as "Mailissa", "Simpsons", "Kwyjibo", or "Kwejeebo", is a mass-mailing macro virus, hence leading some to classify it as a computer worm.
Today's viruses may also take advantage of network services such as the
World Wide Web, e-mail, and file sharing systems to spread, blurring the line
between viruses and worms. Furthermore, some sources use an alternative
terminology in which a virus is any form of self-replicating malware.
The term comes from the term virus in biology. A computer virus reproduces by
making (possibly modified) copies of itself in the computer's memory, storage,
or over a network. This is similar to the way a biological virus works.
Some viruses are programmed to damage the computer by damaging
programs, deleting files, or reformatting the hard disk. Others are not designed
to do any damage, but simply replicate themselves and perhaps make their
presence known by presenting text, video, or audio messages. Even these
benign viruses can create problems for the computer user. They typically take
up computer memory used by legitimate programs. As a result, they often
cause erratic behavior and can result in system crashes. In addition, many
viruses are bug-ridden, and these bugs may lead to system crashes and data
IMPORTANCE TO KNOW ABOUT VIRUSES
Steps to avoid viruses Nothing can guarantee the security of your computer 100 percent. You can continue to improve your computer's security and decrease the possibility of infection by using a firewall, keeping your system up-to-date, maintaining a current antivirus software subscription, and following a few best practices. Tip: Because no security method is guaranteed, it's important to back up critical files on a regular basis before you encounter a virus or other problems. Steps to help avoid viruses: Avoid opening an e-mail attachment from someone you know, unless you know exactly what the attachment is. The sender may be unaware that it contains a virus. 5. Never open an e-mail attachment from someone you don't know. 4. Subscribe to industry standard antivirus software, such as Windows Live OneCare and keep it current. 3. Visit Microsoft Update and turn on automatic updating. Note: If you've installed Office 2003 or Office XP, Automatic Updates will also update your Office programs. If you have an earlier version of Office, use Office Update. 2. Use an Internet firewall (Note: Windows XP with SP2 has a firewall already built-in and turned on by default). 1.
Methods to avoid detection
In order to avoid dtection by users, some viruses employ different kinds of deception. Some old viruses, especially on the MS-DOS platform, make sure that the "last modified" date of a host file stays the same when the file is infected by the virus. This approach does not fool anti-virus software, however, especially that which maintains and dates Cyclic Redundancy Codes on file changes.
Some viruses can infect files without increasing their sizes or damaging the files. They accomplish this by overwriting unused areas of executable files. These are called cavity viruses . For example the CIH virus, or Chernobyl Virus, infects Portable Executable files. Because those files had many empty gaps, the virus, which was 1 KB in length, did not add to the size of the file.
Some viruses try to avoid detection by killing the tasks associated with antivirus software before it can detect them.
As computers and operating systems grow larger and more complex, old hiding techniques need to be updated or replaced. Defending your computer against viruses may demand that your file system migrate towards detailed and explicit permission for every kind of file access.