Much of the world's transactions, whether it is business or personal, are now done online. From social interaction to keeping track of finances, the Internet is now a very large part of the average citizen's life. The Internet is not without its own set of risks, however. Should you encounter a virus, your private information could become compromised, data destroyed and hardware completely fried. Not all viruses are created equal, however. Some viruses have produced billions of dollars in damages. Here is a look at 10 of the most expensive computer viruses of all time, and how to avoid a similar devastation in the future.
The most devastating computer virus to date is MyDoom, which caused over $38 billion in damages. In addition to being the most expensive virus to date, its effects were far-reaching and fast-moving. When a user was infected with the virus it creates network openings which allowed others to have access to your computer. In addition, the virus also had the ability to open random programs. In 2004, an estimated 25% of all emails had been infected by the virus.

Another harmful and expensive computer virus is SoBig. In 2003, the SoBig virus caused over $37.1 billion in devastation. This fast-spreading virus circulated through email as viral spam, and if exposed, the virus had the capability to copy files, emailing itself to others and causing serious damage to computer software and hardware.

ILOVEYOU is another particularly malicious virus that spread quickly through email, websites and file sharing. The ILOVEYOU virus, or the "Love Letter" worm, affected more than 500,000 systems in 2000 and produced over $15 billion in damages, including $5.5 billion in the first week alone. The virus replicated itself and exposed itself to everyone in the owner's contact list. This virus was a pioneer for other viruses, as it was one of the first to attach to an email.

The Conficker virus caused over $9.1 billion in damages in 2007 and infected millions of computers around the world. The virus scanned computers for weaknesses and vulnerabilities, logged keystrokes and downloaded code from hacker-selected websites and more.

Code Red
One of the most well-known viruses to date is the Code Red virus. It caused over $2 billion in damages in 2001, and had the ability to break into computer networks and exploit weaknesses in Microsoft software. Once the virus infected the machine, it actively looked for other machines on the networks to attack.

The Melissa virus was a particularly slimy virus that sent out infected Microsoft Word documents through Microsoft Outlook, delivering viral messages to everyone listed in the Outlook address book. The messages appeared to be coming from the Outlook owner, but was really the Melissa virus at work. A tell-tale indicator that Melissa had infiltrated your Outlook is if your contacts had received an email from you with the message: "Here is that document you asked for … don't show anyone else." There would be a word document attached, complete with the Melissa virus. In 1999, Melissa caused $1.2 billion in damages.

SirCam was a worm that caused over $1 billion in damages in 2001. This virus had the ability to compromise confidential information, delete items or use up space on your hard drive until there was not enough memory to store anything else.

SQL Slammer
SQL Slammer is a virus that greatly affected banks and caused Internet speed to lag significantly across the globe. SQL Slammer caused an estimated $750 million in damages in 2003, and affected 200,000 computers worldwide.

Nimda is one of the Internet's most widespread viruses and among the costliest as well. The virus caused $635 million worth of damages in 2001 and caused Internet browsing time to slow significantly. Additionally, it could affect a user's email account and send out a read-me file to all contacts listed in the email address book. The virus caused traffic and Internet speeds to slowdown.

Sasser created quite a bit of trouble in 2004 when it piled up $500 million in damages, devastated the British Coast Guard mapping system and caused numerous canceled flights. The creator of Sasser was identified as a teenager from Germany, and was quickly apprehended when one of his "friends" turned him in for a $250,000 bounty posted by Microsoft.

The Bottom Line
While the Internet can be a wonderful resource for doing everything from communicating with friends and colleagues to checking your bank statement, it is not necessarily the safest of places to perform such transactions when viruses are lurking in the midst. Protect yourself and your computer with quality anti-virus software, and continue to browse safely on the Internet.

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