A computer virus is a computer program that can copy itself and infect a computer. The term "virus" is also commonly but erroneously used to refer to other types of malware, including but not limited to adware and spyware programs that do not have the reproductive ability. A true virus can 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.
As stated above, the term "computer virus" is sometimes used as a catch-all phrase to include all types of malware, even those that do not have the reproductive ability. Malware includes computer viruses, computer worms, Trojan horses, most rootkits, spyware, dishonest adware and other malicious and unwanted software, including true viruses. Viruses are sometimes confused with worms and Trojan horses, which are technically different. A worm can exploit security vulnerabilities to spread itself automatically to other computers through networks, while a Trojan horse is a program that appears harmless but hides malicious functions. Worms and Trojan horses, like viruses, may harm a computer system's data or performance. Some viruses and other malware have symptoms noticeable to the computer user, but many are surreptitious or simply do nothing to call attention to themselves. Some viruses do nothing beyond reproducing themselves. More at WikiPedia: http://en.wikipedia.org/wiki/Computer_virus
Worm
A computer worm is a self-replicating malware computer program. It uses a computer network to send copies of itself to other nodes (computers on the network) and it may do so without any user intervention. This is due to security shortcomings on the target computer. Unlike a virus, it does not need to attach itself to an existing program. Worms almost always cause at least some harm to the network, if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer.
Many worms that have been created are only designed to spread, and don't attempt to alter the systems they pass through. However, as the Morris worm and Mydoom showed, the network traffic and other unintended effects can often cause major disruption. A "payload" is code designed to do more than spread the worm–it might delete files on a host system (e.g., the ExploreZip worm), encrypt files in a cryptoviral extortion attack, or send documents via e-mail. A very common payload for worms is to install a backdoor in the infected computer to allow the creation of a "zombie" computer under control of the worm author. Networks of such machines are often referred to as botnets and are very commonly used by spam senders for sending junk email or to cloak their website's address. Spammers are therefore thought to be a source of funding for the creation of such worms, and the worm writers have been caught selling lists of IP addresses of infected machines. Others try to blackmail companies with threatened DoS attacks.
Backdoors can be exploited by other malware, including worms. Examples include Doomjuice, which spreads better using the backdoor opened by Mydoom, and at least one instance of malware taking advantage of the rootkit and backdoor installed by the Sony/BMG DRM software utilized by millions of music CDs prior to late 2005. More at WikiPedia: http://en.wikipedia.org/wiki/Computer_worm
Trojan
A Trojan horse, or Trojan, is malware that appears to perform a desirable function for the user prior to run or install but instead facilitates unauthorized access of the user's computer system. "It is a harmful piece of software that looks legitimate. Users are typically tricked into loading and executing it on their systems", as Cisco describes. The term is derived from the Trojan Horse story in Greek mythology.
Trojan horses may allow a hacker remote access to a target computer system. Once a Trojan horse has been installed on a target computer system, a hacker may have access to the computer remotely and perform various operations, limited by user privileges on the target computer system and the design of the Trojan horse.
Operations that could be performed by a hacker on a target computer system include:
* Use of the machine as part of a botnet (e.g. to perform automated spamming or to distribute Denial-of-service attacks) * Data theft (e.g. retrieving passwords or credit card information) * Installation of software, including third-party malware * Downloading or uploading of files on the user's computer * Modification or deletion of files * Keystroke logging * Watching the user's screen * Wasting the computer's storage space * Crashing the computer
Trojan horses in this way require interaction with a hacker to fulfill their purpose, though the hacker need not be the individual responsible for distributing the Trojan horse. It is possible for individual hackers to scan computers on a network using a port scanner in the hope of finding one with a malicious Trojan horse installed, which the hacker can then use to control the target computer. More at WikiPedia: http://en.wikipedia.org/wiki/Trojan_horse_%28computing%29
If you need any kind of Help related to Virus, Worm or Trojan problems, please Visit SCF "PC Help Center": http://scforum.info/index.php?action=forum
katewinslate:
It is very knowledgeable post. Thanks
algeraadrian:
A virus attaches itself to a program or file so it can spread from one computer to another, leaving infections as it travels. The worm reminds Planning Division and kept the virus. Worms spread from computer to computer, but unlike a virus, has the ability to travel without a Trojan horse action.The man, at first glance seem useful software, but actually damage once installed or run on your computer.
necrodiver:
Thx for the in-dept post =) wasn't really sure what the difference between a worm and a virus hahaha =)
krrjhn:
Thanks i think your information is useful but From when i buy norton antivirus, i never face these type of problems again you may have a look on it!!