Combine the illicit thrill of an exotic dancer with the manipulative genius of a hacker and you have one of the worst computer viruses of all time. Melissa was created by David L. Smith, named for his favorite Friday Night Gal, and released into the world on March 26th, 1999. Posing as an email attachment, the self-replicating virus activated when the malicious attachment was opened, then sent itself to the top 50 people in the email client contact list. The damage was so great that some companies had to shut down email programs until the virus was contained. Smith was convicted, fined $5,000 and spent 20 months in jail. Before Melissa, public knowledge of the detriment of malware was previously unknown.
Ironically named, this love letter was sent from the Philippines in May of 2000 and wreaked havoc on computers around the world. Beginning as an email that claimed the attachment contained honey-filled words from a secret admirer, the subsequent worm that was unleashed worked in multiple ways. After copying itself into several different files and adding new registry keys to the victim’s computer, ILOVEYOU would then download a password stealing application that would email personal data to the hacker’s account. ILOVEYOU then used email and chat clients to send itself to other sources, further perpetuating the cycle. Some sources claim the ILOVEYOU computer virus caused over $10 billion in damages.
Taking advantage of a vulnerability in Windows 2000 and Windows NT operating systems, the Code Red and Code Red II computer worms began to gain traction shortly after their 2001 release. Creating a large botnet by installing backdoors on infected machines, Code Red initiated a DDos (distributed denial-of-service) attack on the White House by commanding all computers within its extensive network to contact its web servers at one time. This act overloaded the servers, rendering them unable to perform their needed actions.
The SQL Slammer, also known as Sapphire, was a computer virus that infected the most heavily used web servers across the US at an alarming rate. In January of 2003, the SQL Slammer caused a number of issues including outages in 911 service in Seattle, crashed the Bank of America’s ATM service, and left Continental Airlines with so many electronic issues that they were forced to cancel flights. Over the course of the computer virus’ extensive life, it caused over $1 billion in damages before antivirus and antispyware software was able to patch the problem.
MS Blast, also known as Blaster or Lovesan, was a computer virus born in 2003 that exploited a known vulnerability in Windows operating systems. The virus quickly spread to hundreds of thousands of PCs and included a personalized message to Bill Gates stating, “Billy Gates why do you make this possible? Stop making money and fix your software!!” Some sources estimate that MS Blast caused between $2 and $10 billion in damage over its tenure.
A relatively new exploit, Sasser, began to infect computers around the world on April 30th, 2004 by taking advantage of non-updated Windows 2000 and Windows XP operating systems. Once a PC was infected with Sasser, the malware would scan the PC for other unprotected computers in its network and replicate onto them. Aside from causing massive damage to the computer, Sasser also made shutting down any computer difficult without cutting off the power source. The same group of black hat hackers that created Sasser also took credit for Netsky, a virus that propagated through an email attachment, causing massive DDoS attacks. At their height, the two viruses were said to have cost tens of millions of dollars in damage, including forcing flight cancellations and delays for Delta Airlines and shutting down satellite communications a few French news agencies.
MyDoom makes the list for its ability to bring prominent search engines to their knees. In February of 2004, the creators of MyDoom released the first phrase of this virus into the world. The worm installed backdoors on computers and initiated a DoS attack. The worm was commanded to stop distributing just short of two weeks after it began. Later that year, MyDoom was released again with greater voracity. Like other viruses of its lot, MyDoom searched email contacts as a method of proliferating. Unlike other viruses, MyDoom also submitted these contacts as a query to search engines like Google in an unprecedented denial of service attack. With millions of search requests from corrupted computers coming in, search engines were significantly slowed and some even crashed.
Known as a computer virus that broke ground, Klez goes down in infamy as one of the most malicious viruses of all time. In late 2001, Klez began infecting computers through email messages that would install, replicate and then send themselves to every contact in the infected computer’s address book. Klez also used a tactic called “spoofing” – putting the names of people from the contact list in the “From” line and sending away – giving the impression that the email messages were coming from someone else. The malicious incarnation carried harmful programs that could function like a normal virus, disable antivirus software, or appear as a trojan. The worst forms of the virus rendered infected computers completely inoperable.
The Nimda worm is well known in the internet security world for being one of the fastest spreading viruses for its time. Nimda spread through the internet with a fierceness that had never been seen, its main target being internet servers. According to some sources, Nimda hit the top of reported internet security attacks only twenty two minutes after being released into the wild. Although personal computers were greatly affected by this worm, its main purpose was to bring the internet to a crawl, targeting some of the world’s most used servers.
The Storm Worm, which has many aliases, debuted in late 2006. This trojan horse spread through emails containing catchy subject matter such as “230 dead as storm batters Europe.” The program installed holes in PCs, although the Storm Worm itself was not the payload. Some versions of the payload turned computers into bots that were remotely controlled for nefarious purposes. Mostly, the Storm Worm was used for spreading spam through the botnet.