Computer viruses are still very much alive and replicating, which is why good computer and network security is very important. The term computer virus is often used to encompass Trojan horses (malicious code, which stops the normal functioning), ransomware (which encrypts files to hold hostage until a ransom is paid), and worms (which spread without human interaction and cause damage to software. Typically, computer viruses are designed to trick users, steal private data or corrupt computers and computer networks.
Here are the ten most noteworthy computer viruses from computing history:
- Pikachu. Incorporating the Pokeman character of the same name, this virus is thought to be the first malware targeting children. Released in June 2000, the virus spread by email. On execution, it was designed to delete two critical Windows directories. Oddly, it asked users if they wanted to go ahead and delete the folders, which is why it did not do more damage than it could have
- SQL Slammer. Created in 2003, the SQL Slammer employed a “just try it” approach, which many researchers thought inefficient. It turned out to be the fasted spreading worm in history and brought down bank ATMs, corporate networks and personal computers in record time. The worm was made possible by a software security vulnerability first reported in 2002. Microsoft issued a patch six months before the worm was released but the patch had not been propagated adequately.
- ILOVEYOU. Spread in 2000 via an email message with the subject ILOVEYOU and an attachment LOVE-LETTER_FOR-YOU.txt.vbs. Unwitting recipients clicked on the attachment and activated the visual basic script, which damaged the local machine by overwriting files. To ensure the continued spread, it sent copies of itself to contacts in the address book.
- MacMag. This virus was designed to display a message, “RICHARD BRANDOW, publisher of MacMag, and its entire staff would like to take this opportunity to convey their UNIVERSAL MESSAGE OF PEACE to all Macintosh users around the world” and then delete itself. The date of origin is unknown, but it was discovered in the wild in 1988. Intended to cause no harm, it is ironic that bugs in the virus caused macintosh computer system crashes and file deletion.
- Ika-tako. First reported in May 2021, the Ika-Tako virus disguised itself in music file downloads. Playing the files resulted in the malware infecting computer hard drives and replacing files with pictures of a quid, octopus or ear urchin. On his arrest the hacker, Masato Nakatsuiji, supposedly told police that he wanted to see how much his computer programming skills had improved since the last time he was arrested.
- Stuxnet. Thought to have been in development since 2005, the Stuxnet virus was active from 2010. The virus targeted programme logic controllers (PLCs) used in the automation of electromechanical processes and industrial machinery. Thought to have been created by the U.S. National Security Agency, the CIA and Israeli Intelligence as a tool to disrupt Iran’s nuclear facilities.
- Code Red. The first virus to target enterprise networks successfully in 2001. Code Red installs itself on web servers and then attacks websites by flooding them with requests until they fail. It was unusual in that it could run entirely in memory, leaving no trace. Then worm was named by the researchers who found it as they were drinking Code Red Mountain Dew at the time of discovery.
- Nimda. First appearing in 2001, the Nimda virus affected users of Windows 95, 98, ME, NT 4 and 2000. It was the first virus to modify existing websites so as to offer infected files for download. It had a 4-step life cycle; 1) file infection 2) mass mailing 3) web worm and 4) LAN propagation. It is thought to have infected 150,000 computers in the US in the fiorst 24 hours.
- Commwarrior. Dating from 2005, CommWarrior first appeared in Russia. It was the first mobile phone worm to send copies of itself via MMS messages to all users on an infected phone. CommWarrior did not cause damage to the phone or operating system but resulted in unwanted billing on infected phones.
- Welchia. Also know as the Nachi, Welchia is a so-called nematode worm designed to remove the Blaster virus, a malicious worm. Welchia also patched the Microsoft vulnerabilities that allowed the Blasteer worm to infect in the first place. Ultimately, Welchia deleted itself. Most viruses are designed to destruct, whereas Welchia appears to be a benevolent virus. This notion is controversial in the antiviral industry, which is strongly against the idea that viruses can be beneficial.