A computer virus is a program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes. Viruses can also replicate themselves. All computerviruses are man-made. A simple virus that can make a copy of itself over and over again is relatively easy to produce. Even such a simple virus is dangerous because it will quickly use all availablememory and bring the system to a halt. An even more dangerous type of virus is one capable of transmitting itself across networksand bypassing security systems
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1. ILOVEYOU
The ILOVEYOU virus comes in an e-mail note with “I LOVE YOU” in the subject line and contains an attachment that, when opened, results in the message being re-sent to everyone in the recipient’s Microsoft Outlook address book and, perhaps more seriously, the loss of every JPEG, MP3, and certain other files on the recipient’s hard disk.
2. Code Red
The worm targeted computers with Microsoft IIS web server installed, exploiting a buffer overflow problem in the system. It leaves very little trace on the hard disk as it is able to run entirely on memory, with a size of 3,569 bytes. Once infected, it will proceed to make a hundred copies of itself but due to a bug in the programming, it will duplicate even more and ends up eating a lot of the systems resources.
via F-Secure
The most memorable symptom is the message it leaves behind on affected web pages, “Hacked By Chinese!”,
3. Melissa
Named after an exotic dancer from Florida, it was created by David L. Smith in 1999. It started as an infected Word document that was posted up on the alt.sex usenet group, claiming to be a list of passwords for pornographic sites. This got people curious and when it was downloaded and opened, it would trigger the macro inside and unleash its payload. The virus will mail itself to the top 50 people in the user’s email address book and this caused an increase of email traffic, disrupting the email services of governments and corporations. It also sometimes corrupted documents by inserting a Simpsons reference into them.
4. Sasser
The worm took advantage of a buffer overflow vulnerability in Local Security Authority Subsystem Service (LSASS), which controls the security policy of local accounts causing crashes to the computer. It will also use the system resources to propagate itself to other machines through the Internet and infect others automatically.
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5. Zeus
Zeus is a Trojan horse made to infect Windows computers so that it will perform various criminal tasks. The most common of these tasks are usually man-in-the-browser keylogging and form grabbing. First identified in 2009, it managed to compromise thousands of FTP accounts and computers from large multinational corporations and banks such as Amazon, Oracle, Bank of America, Cisco, etc. Controllers of the Zeus botnet used it to steal the login credentials of social network, email and banking accounts.
6. Conficker
Also known as Downup or Downadup, Conficker is a worm of unknown authorship. It infects computers using flaws in the OS to create a botnet. The malware was able to infect more than 9 millions computers all around the world, affecting governments, businesses and individuals.
The worm works by exploiting a network service vulnerability that was present and unpatched in Windows. Once infected, the worm will then reset account lockout policies, block access to Windows update and antivirus sites, turn off certain services and lock out user accounts among many. Then, itproceeds to install software that will turn the computer into a botnet slave and scareware to scam money off the user. Microsoft later provided a fix and patch with many antivirus vendors providing updates to their definitions.
7. Stuxnet
A virus created for the purpose of cyberwarfare, as it was intended to disrupt the nuclear efforts of the Iranians. It was estimated that Stuxnet has managed to ruin one fifth of Iran’s nuclear centrifuges and that nearly 60% of infections were concentrated in Iran.
The computer worm was designed to attack industrial Programmable Logic Controllers (PLC), which allows for automation of processes in machinery. It specifically aimed at those created by Siemens and was spread through infected USB drives. If the infected computer didn’t contain Siemens software, it would lay dormant and infect others in a limited fashion as to not give itself away. If the software is there, it will then proceed to alter the speed of the machinery, causing it to tear apart. Siemens eventually found a way to remove the malware from their software.
8. Mydoom
Surfacing in 2004, Mydoom was a worm for Windows that became one of thefastest spreading email worm since ILOVEYOU.
It contains the text message, “andy; I’m just doing my job, nothing personal, sorry,”
via Virus.Wikidot.com
The worm spreads itself by appearing as an email transmission error and contains an attachment of itself. Once executed, it will send itself to email addresses that are in a user’s address book and copies itself to any P2P program’s folder to propagate itself through that network. The payload itself is twofold: first it opens up a backdoor to allow remote access and second it launches a denial of service attack on the controversial SCO Group. It was believed that the worm was created to disrupt SCO due to conflict over ownership of some Linux code.
9. CryptoLocker
The ransom operation was eventually stopped when law enforcement agencies and security companies managed to take control part of the botnet operating CryptoLocker and Zeus. Evgeniy Bogachev, the ring leader, wascharged and the encryption keys were released to the affected computers. From data collected from the raid, the number of infections is estimated to be 500,000, with the number of those who paid the ransom to be at 1.3%, amounting to $3 million.
10. Flashback
Though not as damaging as the rest of the malware on this list, this is one of the few Mac malware to have gain notoriety as it showed that Macs are not immune. The Trojan was first discovered in 2011 by antivirus company Intego as a fake Flash install. In its newer incarnation, a user simply needs to have Java enabled (which is likely the majority of us). It propagates itself by using compromised websites containing JavaScript code that will download the payload. Once installed, the Mac becomes part of a botnet of other infected Macs.
ANTIVIRUS
Anti-virus software is a program or set of programs that are designed to prevent, search for, detect, and remove software viruses, and other malicious software like worms, trojans, adware, and more.
SOURCES:
http://www.hongkiat.com/blog/famous-malicious-computer-viruses/
https://www.webroot.com/us/en/home/resources/tips/pc-security/security-what-is-anti-virus-software
http://www.webopedia.com/TERM/V/virus.html
http://searchsecurity.techtarget.com/definition/ILOVEYOU-virus
http://virus.wikia.com/wiki/CodeRed
Serjim 