Top 5 Worst Computer Viruses – You should know

Getting infected with a malicious file is something that has happened to all computer operators at least once, in one fashion or the other. For most people, the situation is quite mild, requiring only a simple clean up, by installing and running a full virus scan of their system. But in other cases, the situation can be disastrous, with the computer completely bricking your system, which no antivirus software can protect your system from.

In this article, I will highlight some of the worst computer viruses in history, viruses that have caused a considerable amount of damaged to peoples and property.

This article will include all malicious files that include Trojan horses and worms. To date, these malicious files have been responsible for a considerable amount of damage, numbering in the billions.

Here are the ten worse computer viruses:

Top 5 Worst Computer Viruses


The ILOVEYOU virus was known for being one of the widest spread in history, this virus was successful in wreaking havoc on millions of computer systems all over the world, causing an estimated $10 billion in damages. Estimates put the infected at 10% of the whole internet population at the time. This virus was so bad, that large corporations were forced to put their mailing systems offline, just to prevent it from infecting them.

Two Filipino programmers, Onel de Guzman and Reonel Ramones were found responsible for its creation. It worked by applying social engineering in order to get people to click on the attachment, in this case, it was a confession of love. The attachment, however, was a script disguised as a text document. Windows inability to show file extensions on attachments at the time was what they used to deceive the masses.

Once you clicked on it, it would send itself to everyone on your mailing list, while overwriting your computer files, replacing them with its self, thus making your system unbootable. The two programmers were never sentenced in a court of law, primarily because malware laws didn’t exist back then. However, this one single event led to the eCommerce law.

2. The Concept Virus

The Concept virus, as it was known, was shipped accidentally on a CD-ROM which was supplied by Microsoft way back in 1995. This was the first virus to actually infect Microsoft Word. Within just a couple of days, a significant amount of the computer user population was infected with this virus. The virus itself took advantage of people’s tendency to share documents across the internet.

3. The Anna Kournikova Worm

The Anna Kournikova worm was created and disguised as a picture of the tennis player. The worm was created by Jan de Wit, who was an obsessed admirer of her. He was eventually arrested and given a community service sentence.

4. Code Red

Code Red first arrived in 2001 and was discovered by two security employees at eEye Digital. The virus was named Code Red, because the two security guards were drinking Code Red Mountain Dew when they first discovered it. The worm worked by exploiting vulnerabilities in the buffer overflow problem of computer systems that had Microsoft IIS web server installed. The worm ran entirely on memory, which means little to no trace of it was left on the system. Its file size was around 3 bytes, to its advantage and once it got onto your system, it would proceed to replicate itself while at the same time consuming more and more system resources.

It would then launch a DoS or Denial of Service attack on several IP addresses which were widely used by the White House. It would also allow the hacker to gain backdoor access to a server. One of the most memorable things about it was the message it left on web pages that it had hacked “Hacked by Chinese!” This message went on to become a meme itself. A patch was eventually released which counter the worm, but by that time, it had already caused $2 billion in damages, due primarily to losses in productivity. The worm affected an estimated 1 – 2 million servers, which was a considerable amount, especially when you consider the fact that there were only 6 million IIS servers at that time.

5. Netsky and Sasser

The Netsky and Sasser worms were written by German teenager Seven Jaschan who was eventually caught and arrested. At the time of his arrest, he was found to be responsible for more than 70% of all the malware circulating the internet at the time, but was fortunate to escape prison time, later going on to be hired by a security company as an ethical hacker.

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