Dangerous Computer Viruses!
5. WannaCry
Dangerous Computer Viruses!
Discovered in May 2017, WannaCry is one of the most infamous ransomware strains ever. Like most ransomware, WannaCry was designed to encrypt files on infected computers and demand a ransom from its victims. However, the malware was unique in that it spread rapidly throughout computer networks by exploiting vulnerabilities in outdated Windows operating systems.
The ransomware infected over 230,000 computers in more than 150 countries and caused billions of dollars worth of damages to healthcare institutions and major corporations. Financial damages from WannaCry have been estimated to be over $4 billion, and new strains of ransomware are still being developed based on its code.
4. Zeus
Zeus is a Trojan horse designed to steal personal financial data such as passwords and bank details. It was first discovered in 2007 and roped infected devices into a botnet, a large network of computers controlled by hackers. Cybercriminals used the botnet to steal money from major corporations and banks. The documented financial damage from the Zeus Trojan was estimated to be around $70 million, but experts believe that costs associated with recovery could be significantly higher.
3. Mydoom
Mydoom is arguably the worst malware in history, causing more than $38 billion worth of damages in 2004. Like Sobig, it was another type of mass mailing computer worm that stole email addresses from infected computers and sent itself to those addresses. The worm was also capable of using the entire network of infected computers to launch distributed denial-of-service (DDoS) attacks, which essentially flood target websites and servers with so much traffic that they become inoperable. Mydoom is actually still alive today, being used in a small portion of modern phishing campaigns.
2. Klez
The Klez malware appeared in October 2001. It had the capability to exploit buggy Microsoft email clients and spread itself to everyone in a user's Outlook address book. Even worse, it had the potential to become a "polymorphic" virus, which means that it could keep changing its code to avoid detection by antivirus software. Many cybercriminals developed different variants of the Klez worm, making it extremely troublesome to deal with. The worm was able to infect around 7 million computers, resulting in damages costing tens of billions of dollars worldwide.
1. ILOVEYOU
ILOVEYOU, also known as the love letter or the LoveBug virus, was first discovered in May 2000. The malware was delivered to millions of users as an email attachment with the subject line “ILOVEYOU.” Once opened, it spreads to every contact in a user's Microsoft Outlook address book and overwrote certain files (eg, JPEG and MP3 files) from the hard drive.
Considering how many organizations relied on Outlook for all their email needs at the time, ILOVEYOU was fairly widespread. According to a retrospective report, the virus affected over 45 million computers within 10 days, resulting in approximately $10 billion in damages.
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