The 10 Most Dangerous Computer Viruses

Computer viruses can vary in severity, ranging from a slight inconvenience to catastrophic.

16:24 16 August 2021

Anyone that has a personal computer is probably aware of the malware known as the computer virus. These attachments can vary in severity, ranging from a slight inconvenience to catastrophic. Some viruses can pose such a significant problem that no level of antivirus can fix it. That’s why preventative action is so necessary. It keeps your computer running smoothly and blocks viruses at the source.

 

To help you understand just how dangerous computer viruses can be, these are ten of the most damaging computer viruses ever circulated on the globe.

 

1. ILOVEYOU

Considered one of the most viral computer viruses ever created, this virus tricked users into opening the email with a proclamation of love. During prime infection, many governments and corporations took the mailing system offline to prevent transmission. Computer system damage was approximately $10 billion worldwide, involving 10% of the world’s computers.

 

Users receiving the virus were encouraged to open the attachment, attached to an email as a TXT file. Unfortunately, Windows was hiding the actual file extension (the virus). Once clicked, the user’s mailing list is automatically sent the file. 

 

This virus highlights why a search for people online is essential. If you don’t recognize a user’s first and last name, investigating who they are can potentially save you the cost of repair or replacing a computer.

This virus lead to the creation of E-Commerce Law, as before this, no formal law existed to prosecute individuals causing such extensive damage criminally. 

 

2. Code Red

Initially discovered in 2001 by two eEye Digital Security employees, this worm virus targeted computers with Microsoft IIS web servers. Unfortunately, there was a buffer overflow problem in the system, leaving very minimal space on the hard disk. Once a computer is infected, the virus begins making hundreds of duplicate copies of itself, eating most of the system’s resources.

 

The virus then overwrites files within itself. Finally, a denial of service is launched on several IP addresses. It can give backdoor access to the server, giving remote access to the machine.

 

Arguably the most remarkable side effect of the virus is the message it leaves behind on all affected web pages, “Hacked By Chinese!”. Ultimately, a patch was released to resolve these issues, but an estimated $2 billion was lost in productivity. Between 1-2 million servers were impacted by the virus.

 

3. Sasser Virus

This Windows worm was first discovered in 2004. Created by Sven Jaschan, the effects of this virus were minimal in cost, but millions of computers were infected. The Sasser virus caused a slowing of the computer, eventually crashing it. It also made it difficult to reset the computer without cutting the power entirely. More than a million machines were infected, including airlines, transit, and hospitals. The damage from the virus was approximately $18 billion. 

 

4. Melissa

This virus was created by David Smith in 1999. Melissa started as an infected word file, originally shared on the alt.sex group. It claimed to be a comprehensive list of passwords for pornographic sites. People would download the word file and open it. The virus would mail itself to the first 50 users in an email address book, causing an increase in email traffic. This disrupted the services of corporations and governments alike. Occasionally, it also corrupted documents by inserting television references into them.

 

 Reportedly, this virus caused $80 million in damages. Mr. Smith was eventually caught and agreed to work with the FBI in capturing other malware creators. Most notably, he aided in capturing the creator of the Anna Kournikova virus. Due to his cooperation in capturing others, he served 20 months in jail, along with a $5000 fine. 

 

5. Stuxnet

Rumors are surrounding the development of this virus, attaching ownership to the Israeli Defence Force, along with the American Government. This was meant to be used as cyber warfare. The intention was to disrupt the nuclear effort of the Iranians.

 

Nearly 60% of this virus was concentrated in Iran, with the damage amounting to one-fifth of the nuclear centrifuges disrupted. The computer worm targeted PLC (Programmable logic controllers), the component responsible for machinery automation. 

 

Spread through infected USB drives, it altered the speed of the machinery, effectively tearing the machine apart. 

 

6. Conficker

While it’s uncertain who created this worm virus, it first originated in 2008. It uses flaws in the OS system to create a botnet, a type of malware. Once the network service vulnerability is exploited, it will reset all account lockout policies. It also blocks access to antivirus software and prevents Windows updates. It was one of the largest worms to surface, with the infection causing an estimated $9 billion in damages.

 

7. Zeus Virus

This trojan horse was designed to have Windows computers perform criminal activities. Typically, these were keylogging and form grabbing, infected through phishing scams or drive-by downloads. It compromised thousands of FTP computers and accounts, including Amazon, Cisco, and Bank of America. Essentially, it stole the login details of social network accounts, banking details, and email accounts. Approximately $70 million was stolen, with nearly 25% of the entire US impacted.

 

8. Mydoom

This worm for Windows surfaced in 2004, becoming the fastest spreading email worm since the ILOVEYOU virus. This virus spreads itself as an email attachment, showing as a transmission error. It automatically sends itself to the email addresses in the address book and copies itself to P2P folders. The estimated cost of damages amounted to 38.5 billion and can still be found occasionally active.

 

9. Cryptolocker

A form of Trojan horse ransomware, this virus uses several methods to spread. Once the computer is infected, it will encrypt specific files on the hard drive. It also encrypts any attached storage connected at the time of infection. While removing the ransomware is simple, the files will remain encrypted unless the amount is paid by the deadline. It is estimated that ransom was paid for approximately 1.3% of all infections – amounting to $3 million in damages.

 

10. Flashback

One of the few Mac malware attacks, Flashback, was first discovered in 2011 by an antivirus company. It attempted to download as a fake Flash install, earning itself the name Flashback. Users now need to have Java enabled, using the Javascript code to download the payload. It stays localized to user’s accounts but sits at nearly 600,000 infections.