Computer viruses are a big nightmare that can disrupt your PC’s performance significantly. Image Credit: InsiderMonkey
Computer viruses are a big nightmare that can disrupt your PC’s performance significantly. Image Credit: InsiderMonkey

Computer viruses, as appalling as they may seem, are a big nightmare that can disrupt your PC’s performance significantly. Apparently, they are designed to corrupt your innocent machine making it helpless and sick. Getting marred by a computer virus has happened to most users in one way or the other. Often, it gives a mild inconvenience to users to clean up the machine and install an antivirus program; nonetheless, it can be a complete disaster in other cases, thereby turning your PC into a mess that no antivirus program can protect.

Here are five most dangerous computer viruses of all time:

1. ILOVEYOU
Perhaps the most virulent computer virus ever created, the ILOVEYOU virus managed to wreck PCs all across the world. Infecting almost 10% of the world’s PCs connected to the Internet, the virus caused a total damage of around $10 billion. The virus apparently got transmitted via email with a subject line “ILOVEYOU,” which is a radical human emotion that no one can ignore. To make it even more alluring, the email contained an attachment that read something like this: Love-Letter-For-You.TXT.vbs. The moment someone opened the file, the virus emailed itself to the first 50 contacts available in the PC’s Windows address book.

2. Melissa
Melissa became the breaking news on March 26, 1999, after hitting the new age of emailing. Built by David L, Melissa was spread in the form of an email attachment by the name “list.doc.” When a person clicked upon the attachment, the virus would find the Microsoft Outlook address book and email itself to the first 50 contacts on the list having a message “Here is that document you asked for…donot show anyone else.” Later on, FBI arrested David L and slapped him with a fine of $5000 for creating the wildest virus of its time.

3. My Doom
My Doom hit the malware world in 2004 and spread exponentially through email with random addresses of senders and subject lines. Infecting somewhere around two million PCs, My Doom smashed the cyber world by instigating a tremendous denial of service attack. It transmitted itself via email in a specially deceitful way that a receiver would first consider a bounced error message that read “Mail Transaction Failed.” However, as soon as the receiver clicked upon the message, the attachment executed and the worm transmitted to email addresses found in the user’s address book. It is easy to believe that this mass mailer worm caused a damage of almost $38 billion.

4. Code Red
Taking advantage of the Microsoft Internet Information Server’s flaw, Code Red spread on the network servers in 2001. Here is an amusing fact about this dangerous virus—it didn’t need you to open an email attachment or execute a file; it just required an active Internet connection with which it ruined the Web page that you opened by displaying a text “Hacked by Chinese!” It’s no surprise that this virus devastated nearly $2.6 billion dollars by hitting almost one million PCs. And in less than a week’s time, the virus brought down over 400,000 servers that included the White House Web server as well.

5. Sasser
Sasser was a Windows worm that was discovered in 2004. Apparently, it would slow down and crash the PC, making it even hard to reset without cutting the power. And its effects were surprisingly troublesome as well, with millions of PCs being infected and crucial, significant infrastructure affected. The worm played on a buffer overflow susceptibility in Local Security Authority Subsystem Service (LSASS) that monitors the safety policy of local accounts causing crashes to the PC. The devastating effects of the virus were massive resulting in over a million infections. This included critical infrastructures, such as new agencies, hospitals, airlines, and public transportation.

[Yahoo]