Throughout the years, there have been quite a few annoying types of computer viruses to get rid of. Although the procedure to remove a virus has become somewhat standardized, that does not mean all virii play by the same rules. Ransomware is a pain the neck to get rid of, but the following viruses have proven to pose quite a challenge as well.

#4 The ILoveYou Virus

Don’t be fooled by the cute name this virus has; it did nothing to reinforce the love bond between computers and their users. In fact, this virus has put quite a few people off when it comes to dealing with computers in general. Launched back in 2000, this was one of the more prominent computer virii to spread via email campaigns.

As one would come to expect from a virus, it is quite capable of doing malicious things. ILoveYou overwrote file names with copies of its own code, allowing it to spread further if the original files were erased. Moreover, it also spread itself to all Outlook contacts automatically. Plus, ILoveYou managed to steal passwords and send them to its creator. This virus caused close to US$15bn in damages, as it infected a significant amount of Fortune 100 clients at that time.

#3 Nimda

One of the main things about Nimda that stood out was how it was launched one week after the 9/11 attacks. At that time, it was believed that this virus was part of a terrorist attack, but the FBI refuted those claims with ease. However, it was the fastest spreading malware of 2001 and 2002. Getting infected with Nimda was not difficult, as it was spread through spam campaigns and over Wifi connections, and could piggyback on other malicious software infiltrating a system.

Even though the damage done by Nimda was somewhat limited to US$635m, it was capable of crashing various Internet networks all over the world. Things got out of hand so fast that a Florida Federal court had to resort to paper communication when their system was infected. This is a very nasty piece of software, to say the least.

#2 Sasser

As the name suggests, Sasser was quite the Sassy computer virus. It even shut down one in three Taiwanese post offices at its peak. Additionally, it delayed British Airway flights and caused roughly US$500m in damages. Distribution of this virus was somewhat new, as it did not require users to open an email attachment. In fact, the virus scanned IP addresses and infiltrated systems once it found a vulnerable host.

#1 Mydoom

Virtually everyone who used a computer in 2004 has heard of the Mydoom virus, which caused a whopping US$38bn in damages. Any computer infected with the virus would become part of a DDoS botnet, attacking specific sites. It is estimated that Mydoom was successfully infecting one user for every 12 emails sent out with this payload.

But that was only the beginning, as Mydoom succeeded in crashing several search engines due to a flood of search requests. Between 600,000 and 700,000 computers have been infected when this virus ran rampant, which was quite an astonishing number at that time. The one thing to remember about this computer virus is how it slowed down global internet access by close to 10%.

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