What Is Computer Worm ?

A computer worm is a self-replicating computer program that penetrates an operating system with the intent of spreading malicious code. Worms utilize networks to send copies of the original code to other computers, causing harm by consuming bandwidth or possibly deleting files or sending documents via email. Worms can also install backdoors on computers. Many worms that have been created are designed only to spread, and do not attempt to change the systems they pass through. However, as the Morris worm and Mydoom showed, even these "payload-free" worms can cause major disruption by increasing network traffic and other unintended effects.

Worms are often confused with computer viruses; the difference lies in how they spread. Computer worms self-replicate and spread across networks, exploiting vulnerabilities, automatically; that is, they don’t need a cybercriminal’s guidance, nor do they need to latch onto another computer program. As such, computer worms pose a significant threat due to the sheer potential of damage they might cause. A particularly notorious incident occurred in 1988. A computer worm since named the Morris worm caused hundreds of thousands, if not millions, of dollars in damage, and its creator was convicted under the Computer Fraud and Abuse Act.

Different Types Of Computer Worms :-

Email Worms :-

Email Worms spread through infected email messages as an attachment or a link of an infected website. Email worms uses a PC's email client to spread itself. It will either send a link within the email that, when clicked, will infect the computer, or it will send an attachment that, when opened, will start the infection. Once the worm is installed, it will search the host computer for any email addresses contained on it. It will then start the process again, sending the worm without any input from the user.

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Instant Messaging Worms :-

Instant Messaging Worms spread by sending links to the contact list of instant messaging applications.These work in a similar way to email worms. The infected worm will use the contact list of the user's chat-room profile or instant-message program to send links to infected websites. These are not as effective as email worms as the recipient needs to accept the message and click the link. They tend to effect only the users of the particular program.

Internet Worms :-

Internet worm will scan all available network resources using local operating system services and/or scan the Internet for vulnerable machines. If a computer is found vulnerable it will attempt to connect and gain access to them.Internet worms are completely autonomous programs. They use an infected machine to scan the Internet for other vulnerable machines. When a vulnerable machine is located, the worm will infect it and begin the process again. Internet worms are often created to exploit recently discovered security issues on machines that haven't installed the latest operating-system and security updates.

File-sharing Networks Worms :-

File-sharing Networks Worms place a copy of them in a shared folder and spread via P2P network.  File-sharing worms take advantage of the fact that file-sharers do not know exactly what they are downloading. The worm will copy itself into a shared folder with an unassuming name. When another user on the network downloads files from the shared folder, they will unwittingly download the worm, which then copies itself and repeats the process. In 2004, a worm called "Phatbot" infected millions of computers in this way, and had the ability to steal personal information, including credit card details, and send spam on an unprecedented scale.