The Morris Worm was a self-replicating computer program (worm) written by Robert Tappan Morris, a student at Cornell University, and released from MIT on November 2, 1988.

It unintentionally caused denial-of-service (DoS) for around 10% of the 60,000 machines connected to ARPANET in 1988.


Released in September 2013, CryptoLocker spread through email attachments and encrypted the user’s files so that they couldn’t access them. This was one of the worst malware which asks money to release your files. It was called Ransomware. With 500,000 victims, CryptoLocker made upwards of $30 million in 100 days. Yatron Ransomware, the latest one, encrypts targeted files and delete encrypted files if the victim fails to make payment within 72 hours.


This is one of the most well-known and destructive viruses of all time. In 2000 it was the most damaging malware event of all time. The virus was sent The malware was a worm that was downloaded by clicking on an attachment called ‘LOVE-LETTER-FOR-YOU.TXT.vbs’. in an email with a subject line that said: “I love you”.


This is a record-holder malware and was the fastest-spreading email-based worm ever.MyDoom hit tech companies like  Microsoft, and Google with a Distributed Denial of Service (DDS) attack. MyDoom spammed junk mail through infected computers, with the text that said “andy; I’m just doing my job, nothing personal, sorry”.

5. Trojan

A Trojan horse or Trojan is a type of malware that is often disguised as legitimate software. Trojans can be employed by cyber-thieves and hackers trying to gain access to users’ systems. Users are typically tricked by some form of social engineering into loading and executing Trojans on their systems. Once activated, Trojans can enable cyber-criminals to spy on you, steal your sensitive data, and gain backdoor access to your system. Astaroth Trojan emerged as the latest computer virus in 2017. It targets antivirus tools to steal username and passwords. Trojan Glupteba is another worst computer virus that has several variants with different functionalities.


A network worm that attacks Microsoft Windows, Mac OSX and Linux platforms. It spreads via social networking sites like FaceBook, Twitter, Skype, etc. It spreads through the fake video player. If you click on one of the links which Koobface has posted online, you’ll end up at a web page – typically a fake YouTube or Facebook Video page.

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