Topic: What is Virus, Worm and Trojan ?!

[Amker]

Virus

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!!

[hillaryjohnson]

The biggest danger with a worm is its capability to replicate itself on your system, so rather than your computer sending out a single worm, it could send out hundreds or thousands of copies of itself, creating a huge devastating effect. One example would be for a worm to send a copy of itself to everyone listed in your e-mail address book. Then, the worm replicates and sends itself out to everyone listed in each of the receiver's address book, and the manifest continues on down the line.

[unixinfoservice]

Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation. And Computer worms are programs that reproduce, assassinate apart and biking beyond the arrangement connections. Trojan horses are a austere affair because of the ascent calmness of character annexation and the importance of protecting the privacy of sensitive information. There are a lot of anti-virus programs you can choose from which will enable you to protect your computer.

[Payam20]

thanks....

[Blake_Brice]

Trojan - A program that has been designed to appear innocent but has been intentionally designed to cause some malicious activity or to provide a backdoor to your system.

Virus - A program that when run, has the ability to self-replicate by infecting other programs and files on your computer. These programs can have many effects ranging from wiping your hard drive, displaying a joke in a small box, or doing nothing at all except to replicate itself. These types of infections tend to be localized to your computer and not have the ability to spread to another computer on their own. The word virus has incorrectly become a general term that encompasses trojans, worms, and viruses.

Worm - A program that when run, has the ability to spread to other computers on its own using either mass-mailing techniques to email addresses found on your computer or by using the Internet to infect a remote computer using known security holes.