14.-+Virus

Definition: "A parasitic program written intentionally to enter a computer without the users permission or knowledge. The word parasite is used because a virus attaches to files or boot sectors and replicates itself, thus continuing to spread. Though some virus's do little but replicate others can cause serious damage or effect program and system performance. A virus should never be assumed harmless and left on a system." -Symantec
 * What is a virus? **

A functional definition of a computer virus must include the fact that Ø it creates damage to the computer system This definition is somewhat simplified and does not cover all virus types, but is sufficient to show the major differences between viruses and so-called: Ø "Trojan" programs, which is that the virus replicates, but the Trojan program does not.

Five most common types: 1). Macro virus - this type of virus usually comes as part of a document or spreadsheet, often in email. 2). Boot sector virus - this type of virus overwrites the boot sector on your hard drive or floppy drive. 3). File infector virus - this type of virus attaches itself to executables, for example .com and .exe files. 4.) Stealth virus - this type of virus tries to fool antivirus software by catching its requests to the operating system (asking to open a file, for example). 5). Self-modifying virus - this type of virus was designed to avoid detection by antivirus software by changing itself internally.