How To Clean Out Viruses From Computer For Free

What are the top 10 computer viruses of all time?

Updated: 04/12/2021 by Computer Hope

Viruses come in many forms and are created with different intentions. Some corrupt or delete a computer files while others are designed to replicate until they use your RAM; rendering your computer unable to operate. There are even viruses, like Ping-Pong that are created as a joke and do not cause any real damage.

To date, there over one million computer viruses exist, but only a small percentage of them are in mass circulation. Only a few have created havoc and fiscal cost at the level of those viruses listed on this page.

Ten of the most prolific viruses of all time

The following are some of the viruses that resulted in widespread computer infections.

Storm Worm (also called Peacomm and Nuwar)

On January 19th, 2007, over 200 million e-mails included links to download the Storm Worm, which help play a part in the overall attack. Most believe the worm gets its name from the fact that one of the e-mail messages carrying the virus had "230 dead as storm batters Europe" as its subject.

Different than the W32_Storm_Worm released in 2001, this virus was released and identified in late 2007.
Allowed hackers to control the computer remotely, using it for malicious activity, like sending mass amounts of e-mail (spam).
Propagated through fake links to videos and news stories.

Netsky and Sasser

Netsky spread via e-mail and Windows networks, creating large amounts of Internet traffic and causing Denial of Service (DoS) attacks. At the time, Netsky and its variants were believed to be responsible for as many as 25% of all virus infections. Sasser replicated by finding other systems with vulnerabilities and forcing them to download the virus. Once on a new machine, it altered the operating system to make it difficult for users to shut down their computer.

Released in February and April 2004 respectively.
Created by 17-year old Sven Jaschan.
One of the few viruses to be tracked back to their creator.

MyDoom

This worm was unique in that it had a timer of sorts. The virus started Denial of Service attacks, then stopped distributing itself 11 days later. These attacks were aimed at various Internet servers, including attacks against search engines, causing several of them to crash and others to return search results much slower than normal.

Released on February 1st, 2004.
Replicated using e-mail and peer-to-peer networks.
Created backdoor that stayed open even after the worm stopped distributing itself.

Blaster Worm

Once this worm got onto a network, it spread quicker because firewalls often didn't block internal machines from using a port the worm utilized. It was stopped by filtering by ISPs and public awareness.

Released in August 2003, original creator is unknown.
Infected millions of computers worldwide.
Launched Denial of Service (DoS) attacks against Microsoft servers.

SQL Slammer

A prolific web server virus, the Slammer (also known as Sapphire) infected nearly half of the servers that help run the Internet 15 minutes after its initial attack.

Released in January 2003.
Affected computer networks and systems, causing shutdowns and a range of damage estimated at over $1 billion.
Caused disruptions in Bank of America ATM service, and in Seattle's 911 services.

Nimda

Spreading through e-mail and Web pages, this worm targeted Internet servers, slowing Internet performance nearly to a halt. It also opened a backdoor to the computer's operating system, allowing a hacker access to the computer. However, access was limited by user account permissions.

Released in 2001.
Name is the word "admin" spelled backward.
Fastest spreading computer virus in history.

Code Red / Code Red II

These viruses exploited a vulnerability in Microsoft Windows 2000 and NT, causing a buffer overflow. Code Red initiated Denial of Service attacks against White House web servers, while Code Red II opened a backdoor for hackers to access Windows 2000 systems.

Released in summer 2001.
Later blocked from spreading by Microsoft patch.

Klez

This virus was unique in that hackers reproduced in many forms. It was also capable of spoofing to help spread the virus as recipients would think it was coming from a friend.

Released in late 2001.
Distributed through e-mail.
Capable of disabling antivirus programs and making a computer unusable.

ILOVEYOU

Traveled through e-mail as a message from a secret admirer. When users downloaded the attachment called WIN-BUGSFIX.EXE, the virus would copy and embed itself in key files; including registry keys.

Suspected to be created by Onel de Guzman (Philippines) in 2000.
Initially spread through e-mail and later through IRC clients.
Damage caused by the virus was estimated at around $10 billion.

Melissa

Once activated, the virus would replicate and then sends itself out to the first 50 people in the address book of the recipient.

Created by David Smith in 1999.
Created a mess for government and public sector networks.
Caused some e-mail providers to shut down e-mail services until the virus was contained.