COMPUTER VIRUS,TROJAN -KNOWN AND UNKNOWN FACTS

WHAT IS A VIRUS ?


A virus is a program that replicates itself. It spreads by making copies of


itself on a computer or by inserting computer code into program or operating


system files. Viruses don't always damage files or computers, but they


usually affect a computer's performance and stability. For a virus to infect


a computer or to spread, you usually have to do something, such as open an


infected e‑mail attachment.








ARE ALL VIRUSES HARMFUL?






Yes, to varying degrees. Virus damage can range from slowing computer


performance to a loss of information and programs. In the worst case, viruses


delete or modify information and programs on your computer. Some e‑mail


viruses send confidential information in messages when spreading. Even when a


virus is not directly damaging information, the process of replication can


slow your computer and Internet connection.






WHAT IS WORM?


A worm is computer code that spreads without user interaction. Most worms


begin as e‑mail attachments that infect a computer when they're opened. The


worm scans the infected computer for files, such as address books, or


temporary webpages, that contain e‑mail addresses. The worm uses the addresses


to send infected e‑mail, and often mimics (or spoofs) the "From" addresses in


subsequent e‑mail messages so that those infected messages appear to be from


someone you know. Worms then spread automatically through e‑mail, networks, or


operating system vulnerabilities, often overwhelming those systems before the


cause is known. Worms aren't always destructive to computers, but they


usually cause computer and network performance and stability problems.




WHAT IS A TROJAN HORSE?


The name comes from the trojan war between sparta and the city of troy according to greek's mythology.In that war sparta made a giant horse ,inside which they hide their soldiers and later by that horse they break in to the troy's empire and destroy the city,like wise trojan in computer is malicious program which is hidden inside another pgm and seems as a useful program or software but actually it harms the computer.............Lipak





A Trojan horse is a malicious software program that hides inside other


programs. It enters a computer hidden inside a legitimate program, such as a


screen saver. It then puts code into the operating system, which enables a


hacker to access the infected computer. Trojan horses do not usually spread


by themselves; they are spread by viruses, worms, or downloaded software




What is a blended threat?


A blended threat is a combination of some or all of the malicious programs


discussed in the sections above. Blended threats often begin when someone


interacts with a virus (such as opening an unsafe e‑mail attachment). The


virus automatically propagates using worm behavior, and then installs a


Trojan horse on the infected computer.






How can I tell if my computer has a virus?


If you can answer "yes" to any of the following questions, your computer


might have a virus.


Is your computer running very slowly? A common symptom of a virus is much


slower than normal computer performance. However, there can be other reasons


for slow performance, including a hard disk that needs defragmenting, a


computer that needs more memory (RAM), or the existence of spyware or adware.


For more information about spyware, see How to tell if your computer is


infected with spyware.


Are you getting unexpected messages, or are programs starting automatically?


Some viruses can cause damage to Windows or some of your programs. The


results of this damage might include messages appearing unexpectedly,


programs starting or closing automatically, or Windows shutting down


suddenly.


Is your modem or hard disk working overtime? An e‑mail virus works by sending


many copies of itself by e‑mail. One indicator of this is that the activity


light on your broadband or external modem is constantly lit; another is the


sound of your computer's hard disk continually working. These are not always


symptoms of a computer virus, but when combined with other problems, can


indicate a virus infection.


To check for viruses, scan your computer with an antivirus program. New


viruses appear every day, so keeping your antivirus program updated is


important.