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Computer viruses differ in their spread types and effects. Some of these viruses, which have many different types, have been effective all over the world and have made a name for themselves.

Computer viruses are malicious software that infiltrate your computers in various ways and make them vulnerable. Some of the viruses, which are often seen in unconscious users, have also managed to affect almost the whole world. Like in the recent WannaCry example. Here are the 5 most famous viruses and their effects on the computer.

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5 Famous Computer Viruses That Have Influenced The Whole World And Its Horrible Effects

Morris Worm

Let's start with one of the most important examples of malware. The Morris Worm was the first malicious program to be covered by the mainstream media because of its massive repercussions. When the dates showed November 2, 1988, the virus was released and within 24 hours an estimated 10 percent of internet-connected computers were infected. The malware slowed thousands of systems by creating files in temporary folders to copy itself.

These affected computers were rendered useless until the software was removed. The effect of the virus lasted for about two days. Naturally, it took even longer to clear from an entire network. For example, the University of California needed 20 working days to completely get rid of the virus on their computers.

But initially the software was not malicious. Robert Tappan Morris created the program as a way to test the size of the internet. It was a coding error that was estimated to cost $53,000 per institution, according to the judge in the case against Morris. According to one estimate, the total cost of the worm is claimed to be between $250,000 and $96 million.

Now one of the world's most famous hackers, Morris was the first to be found guilty under the 1986 Computer Fraud and Abuse Act. Robert Tappan Morris was sentenced to a $10,050 fine and three years in prison. He was also sentenced to 400 hours of community service.

Melissa Virus

Although rumors claimed that the first virus to affect Word was spread via email, this was not true. The virus was actually accidentally spread by professional companies. Microsoft was partially responsible for the events when it shipped Windows 95 Software Compatibility Test CD-ROMs containing viruses.

In March 1999, a Word file was uploaded to the Usenet discussion group, It included a list of passwords for 80 porn websites so you can imagine how many were downloaded. After these processes, the virus is automatically transmitted to the first 50 people in the Microsoft Outlook address book.

The virus was then sent to other Word files, meaning that personal information could be sent to family, friends and colleagues. The software is known to cause an estimated $80 million in damage to private and corporate networks. The Melissa virus is named after a stripper and the software creator, David L Smith, met in Florida.




I Love You Virus

This virus appeared as a worm that spread via an email with the subject line “ILOVEYOU”. Once opened, it sends itself to everyone in the Outlook address book, making it one of the fastest-spreading viruses. It is said to have reached more than 50 million users in 10 days.


What caused more problems was the capacity to overwrite files. If you didn't have backups and you had relatively few personal networks, you had to say goodbye to JPEGs and your audio files. It's estimated that firms in America cost more than $15 billion to keep the worm from expanding.

Mydoom Virus

We are dealing with the fastest spreading email worm. MyDoom and its variants have caused approximately $38.5 billion in losses worldwide. The worm acts on a similar principle to ILOVEYOU. An e-mail with misleading topics such as "Mail Delivery System" contains an attachment that, after being opened, is sent to addresses found in local files. While previous worms targeted a limited number of individuals, MyDoom was non-selective.

The crux of the virus was its ability to leave a backdoor opening in systems for hackers to exploit. Some of these backdoors would stay open and do damage afterwards. DDoS started to be thrown on major sites such as SCO Group and Microsoft. Later versions also affected Google and other search engines, with requests from broken PCs attempting to crash into streaming servers.

Some of its effects are due to its longevity. Although it was first detected in 2004, it was also determined that it was responsible for the cyber attacks carried out in the USA and South Korea in 2009. Its creators have not yet been found, but its origin is known to be Russia. In the message on the worm, “andy; I'm just doing my job, sorry” is used.


When the dates showed May 2017, there was an atmosphere of panic all over the world. WannaCry, a ransomware, has affected many users. Although it lasted only a few days, the ransomware had hit between 200,000 and 300,000 computers worldwide.


The software infiltrates your computer and encrypts all your files and data. Afterwards, it asks you for $600 worth of Bitcoin, but the fact that you paid the money usually doesn't make any sense. Still, some users paid the requested money and only made the hackers rich.

Once infected, the computer screen will lock, a red alert and two countdowns will be displayed, one showing the increase in the ransom demand and the other the time after which the files will be permanently deleted. Fortunately, Microsoft acted quickly by issuing updates to combat the threat. The hackers partially achieved their goal by receiving over $130,600 in payments after the attack.



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