Computer viruses are one of the most common problems computer repair services are called upon to fix. In 2010, Happy Hamster Computers removed more than 60,000 viruses from more than 3,000 computers. It can cost hundreds of dollars to fix an infected computer, and in some instances, computer repair is futile if the data gets destroyed and the hardware fried. The following is a look at some of the most expensive computer viruses to date.

10. Sasser: Appearing in 2004, Sasser affected the British Coast Guard’s mapping system, canceled several flights and caused up to $500 million in damages. The creator was a German teenager.

9. Nimda: As one of the most widespread computer viruses, Nimda caused about $635 million in damages. Computer repair services reported that the 2001 virus affected email accounts and slowed down internet browsing.

8. SQL Slammer: Causing about $750 million in damages in 2003, the SQL Slammer virus reached about 200,000 computers across the globe. It mostly affected banks and caused internet speeds to slow.

7. SirCam: In 2001, the SirCam worm caused just over $1 billion in damages. The worm accessed confidential information and used up space on a computer’s hard drive until the memory was full.

6. Melissa: In 1999, the Melissa virus racked up $1.2 billion in damages. It sent out fake messages to email addresses saved in Outlook users’ address books. The emails looked legit, but the attached MS Word documents infected the computers of recipients who opened it.

5. Code Red: The Code Red virus in 2001 infiltrated computer networks to exploit the weaknesses in their Microsoft software, causing $2 billion in damages.

4. Conficker: Causing $9.1 billion worth of damage in 2007, Conficker infected millions of systems worldwide. It recorded keystrokes, downloaded codes from malicious websites and scanned computers for weaknesses.

3. ILOVEYOU: ILOVE YOU was the “love letter” worm that caused a total of $15 billion in damages. In its first week alone, the devastation cost $5.5 billion! The worm, with its ability to replicate itself and affect contacts saved in email accounts, spread through emails, websites and file-sharing sites.

2. SoBig: The 2003 SoBig virus caused $37.1 billion in damages. The virus had the ability to replicate itself, send viral spam email messages, copy the files within infected computers and damage a computer’s hardware and software.

1. MyDoom: The most expensive computer virus to date is MyDoom, whose devastation cost $38 billion in 2004. It moved from computer to computer quickly, made its way around the world, opened random programs in infected computers and left the computers open for others to access. It infected about 25 percent of the emails sent that year.