A worm automatically replicates itself across the networks and may infect millions of servers in a short period of time. It is conceivable that the cyber-terrorists may use a wide-spread worm to cause major disruption to the Internet economy. Much recent research concentrates on propagation models and early warning, but the defense against worms is largely an open problem. New defense techniques are developed based on the behavioral difference between normal hosts and worm-infected hosts.
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A computer worm is a standalone malware computer program that replicates itself in order to spread to other computers. It will use this machine as a host to scan and infect other computers. When these new worm-invaded computers are controlled, the worm will continue to scan and infect other computers using these computers as hosts, and this behavior will continue.
Many worms 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.
In that novel, Nichlas Haflinger designs and sets off a data-gathering worm in an act of revenge against the powerful men who run a national electronic information web that induces mass conformity. There's never been a worm with that tough a head or that long a tail! On November 2, , Robert Tappan Morris , a Cornell University computer science graduate student, unleashed what became known as the Morris worm , disrupting many computers then on the Internet, guessed at the time to be one tenth of all those connected.
Computer viruses generally require a host program. The virus writes its own code into the host program. When the program runs, the written virus program is executed first, causing infection and damage. A worm does not need a host program, as it is an independent program or code chunk.
Therefore, it is not restricted by the host program , but can run independently and actively carry out attacks. Exploit attacks. Because a worm is not limited by the host program, worms can take advantage of various operating system vulnerabilities to carry out active attacks.
For example, the " Nimda " virus exploits vulnerabilities to attack. When a user accesses a webpage containing a virus, the virus automatically resides in memory and waits to be triggered. There are also some worms that are combined with backdoor programs or Trojan horses , such as " Code Red ".
Worms are more infectious than traditional viruses. They not only infect local computers, but also all servers and clients on the network based on the local computer. Worms can easily spread through shared folders , e-mail s, malicious web pages, and servers with a large number of vulnerabilities in the network. Any code designed to do more than spread the worm is typically referred to as the " payload ".
Typical malicious payloads might delete files on a host system e. This allows the computer to be remotely controlled by the worm author as a " zombie ". Networks of such machines are often referred to as botnets and are very commonly used for a range of malicious purposes, including sending spam or performing DoS attacks. Some special worms attack industrial systems in a targeted manner. Stuxnet does not need to be transmitted through a network connection.
It is a malicious virus written specifically for industrial control systems [ duplication? Although these systems operate independently from the network, if the operator inserts a virus-infected U disk [ definition needed ] into the system's USB interface, the virus will be able to gain control of the system without any other operational requirements or prompts.
Worms spread by exploiting vulnerabilities in operating systems. Vendors with security problems supply regular security updates  see " Patch Tuesday " , and if these are installed to a machine, then the majority of worms are unable to spread to it. If a vulnerability is disclosed before the security patch released by the vendor, a zero-day attack is possible. Users need to be wary of opening unexpected email,   and should not run attached files or programs, or visit web sites that are linked to such emails.
However, as with the ILOVEYOU worm, and with the increased growth and efficiency of phishing attacks, it remains possible to trick the end-user into running malicious code. Anti-virus and anti-spyware software are helpful, but must be kept up-to-date with new pattern files at least every few days. The use of a firewall is also recommended. Users can minimize the threat posed by worms by keeping their computers' operating system and other software up to date, avoiding opening unrecognized or unexpected emails and running firewall and antivirus software.
Infections can sometimes be detected by their behavior - typically scanning the Internet randomly, looking for vulnerable hosts to infect. A helpful worm or anti-worm is a worm designed to do something that its author feels is helpful, though not necessarily with the permission of the executing computer's owner. Beginning with the very first research into worms at Xerox PARC , there have been attempts to create useful worms. Those worms allowed John Shoch and Jon Hupp to test the Ethernet principles on their network of Xerox Alto computers [ citation needed ].
Similarly, the Nachi family of worms tried to download and install patches from Microsoft's website to fix vulnerabilities in the host system by exploiting those same vulnerabilities. Regardless of their payload or their writers' intentions, most security experts [ who? Several worms, including some XSS worms , have been written to research how worms spread, such as the effects of changes in social activity or user behavior.
Anti-worms have been used to combat the effects of the Code Red ,  Blaster , and Santy worms. Welchia is an example of a helpful worm. Welchia automatically reboots the computers it infects after installing the updates. One of these updates was the patch that fixed the exploit. From Wikipedia, the free encyclopedia. This article is about coding of a worm. For the data storage device, see Write once read many. For other uses, see worm disambiguation. Not to be confused with computer virus.
Retrieved 9 September PLOS One. The Shockwave Rider. New York: Ballantine Books. Cases and Materials on Criminal Law. The Seattle Times. Archived from the original on August 26, Retrieved May 18, Archived from the original on Hiese online. Retrieved BBC News. February 23, July Security Studies. Paris, France: Atlantis Press. Retrieved July 5, December 18, Retrieved 9 June Malware topics. Comparison of computer viruses Computer virus Computer worm List of computer worms Timeline of computer viruses and worms.
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DAW : A Distributed Anti-Worm System
A computer worm is a standalone malware computer program that replicates itself in order to spread to other computers. It will use this machine as a host to scan and infect other computers. When these new worm-invaded computers are controlled, the worm will continue to scan and infect other computers using these computers as hosts, and this behavior will continue. Many worms 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. In that novel, Nichlas Haflinger designs and sets off a data-gathering worm in an act of revenge against the powerful men who run a national electronic information web that induces mass conformity.