Computers viruses, worms, ransomware, etc. are kinds of malicious software that no user should take lightly. On several occasions, we have touched upon security steps that each user should take in order to protect its identity and data. Sadly sometimes even when all precautions are taken some malware can still slip through and wreak havoc. Today we are looking at some of the worst or the best, depending on your view that has indeed wreaked plenty of havoc.
10 worst computer viruses in historyIn the list of the 10 most famous computer viruses below, we show the costs, dates, reach, and other key facts. First a note about terms: we use the words “virus” and “worm” interchangeably because most readers search for them that way. But there’s a subtle difference that we explain after the list.
The worst computer virus outbreak in history, Mydoom caused estimated damage of $38 billion in 2004, but its inflation-adjusted cost is actually $52.2 billion. Also known as Novarg, this malware is technically a “worm,” spread by mass emailing. At one point, the Mydoom virus was responsible for 25% of all emails sent.
Mydoom scraped addresses from infected machines, then sent copies of itself to those addresses. It also roped those infected machines into a web of computers called a botnet that performed distributed denial of service (DDoS) attacks. These attacks were intended to shut down a target website or server.
Mydoom is still around today, generating 1% of all phishing emails. That’s no small feat considering the 3.4 billion phishing emails sent each day. By that figure, Mydoom has taken on a life of its own, infecting enough poorly-protected machines to send 1.2 billion copies of itself per year, 16 years after its creation.
Though a $250,000 reward was offered, the developer of this dangerous computer worm was never caught.
Wondering what makes the world’s most secure computers so safe? See the Tech@Work guide: Upgrade to the World's Most Secure and Manageable PC
The 2003 Sobig computer virus is actually another worm. It is second only to the Mydoom virus in its scope. The $30 billion figure is a worldwide total, including Canada, the U.K., the U.S., mainland Europe, and Asia. Several versions of the worm were released in quick succession, named Sobig.A through Sobig.F, with Sobig.F being the most damaging.
This cybercriminal program masqueraded as legitimate computer software attached to emails. It disrupted ticketing at Air Canada and interfered with countless other businesses. Despite its widespread damage, the creator of the successful bug was never caught.
Klez is a close third on the list of the worst computer viruses ever created. With nearly $20 billion in estimated damages, it infected about 7.2% of all computers in 2001, or 7 million PCs. The Klez worm sent fake emails, spoofed recognized senders and, among other things, attempted to deactivate other viruses.
As with other viruses and worms, Klez was released in several variants. It infected files, copied itself, and spread throughout each victim’s network. It hung around for years, with each version more destructive than the last.
Windows has come a long way since most of the computer viruses on this list hit the web. Thankfully, built-in protection with Microsoft Defender is always on the watch.
The year 2000’s ILOVEYOU virus worked by sending a bogus “love letter” that looked like a harmless text file. Like Mydoom, this attacker sent copies of itself to every email address in the infected machine’s contact list. Shortly after its May 4 release, it had spread to more than 10 million PCs.
The virus was created by a college student in the Philippines named Onel de Guzman. Lacking funds, he wrote the virus to steal passwords so he could log into online services he wanted to use for free. He reportedly had no idea how far his creation would spread. This virus is also known as Loveletter.
Need to up your remote work security game before there’s another entry on the list of most deadly computer viruses? See our guide: How to Work Remotely and Securely
The 2017 WannaCry computer virus is ransomware, a virus that takes over your computer (or cloud files) and holds them hostage. The WannaCry ransomware ripped through computers in 150 countries, causing massive productivity losses as businesses, hospitals, and government organizations that didn’t pay were forced to rebuild systems from scratch.
The malware raged like wildfire through 200,000 computers worldwide. It stopped when a 22-year-old security researcher in the U.K. found a way to turn it off. Computers with out-of-date operating systems were hit especially hard. That’s why security experts always recommend updating your systems frequently.
In September 2020, one of the potentially largest computer virus attacks in medical history hit Universal Health Services. The U.S. hospital chain, which has more than 400 locations, was reportedly struck by damaging ransomware. The attack forced the cancellation of surgeries and made healthcare workers switch to paper records.
The Zeus computer virus is an online theft tool that hit the web in 2007. A whitepaper by Unisys three years later estimated that it was behind 44% of all banking malware attacks. By then, it had breached 88% of all Fortune 500 companies, 2,500 organizations total, and 76,000 computers in 196 countries.
The Zeus botnet was a group of programs that worked together to take over machines for a remote “bot master.” It originated in Eastern Europe and was used to transfer money to secret bank accounts. More than 100 members of the crime ring behind the virus, mostly in the U.S., were arrested in 2010. It’s not as prominent today, but some of the virus’ source code lives on in newer botnet viruses and worms.
Zeus caused documented damage of $100 million. But the real cost in terms of lost productivity, removal, and undocumented theft is undoubtedly much higher. A $3 billion estimate, adjusted for inflation, puts this virus at a cost of $3.7 billion in today’s dollars.
First observed in 2001, the Code Red computer virus was yet another worm that penetrated 975,000 hosts. It displayed the words “Hacked by Chinese!” across infected web pages, and it ran entirely in each machine’s memory. In most cases it left no trace in hard drives or other storage.
Financial costs are pegged at $2.4 billion. The virus attacked websites of infected computers and delivered a distributed denial of service (DDoS) attack on the U.S. White House’s website, www.whitehouse.gov. In fact, the White House had to change its IP address to defend against Cod Red.
Can your printer get a virus? See our cool infographic: The State of Printer Security
The SQL Slammer worm cost an estimated $750 million across 200,000 computer users in 2003. This computer virus randomly selected IP addresses, exploiting vulnerabilities and sending itself on to other machines. It used these victim machines to launch a DDoS attack on several internet hosts, significantly slowing internet traffic.
The Slammer worm hit banks in the U.S. and Canada especially hard, taking ATMs offline in many locations. Customers of Toronto’s Imperial Bank of Commerce found themselves unable to access funds. The attack reared its ugly head again in 2016, launching from IP addresses in Ukraine, China, and Mexico.
Thankfully, ransomware attacks like the 2013 CryptoLocker virus have dipped since their 2017 peak. This malware attacked upwards of 250,000 machines by encrypting their files. It displayed a red ransom note informing users that “your important files encryption produced on this computer.” A payment window accompanied the note.
The virus’ creators used a worm called the Gameover Zeus botnet to make and send copies of the CryptoLocker virus. According to a report by security firm Sophos, the average ransomware attack costs a business $133,000. If we estimate that CryptoLocker hit 5,000 companies, that would put its total cost at $665 million.
Where will cybersecurity go next? See our guide: The Future of Cybersecurity
The Sasser worm was written by a 17-year-old German computer science student named Sven Jaschan. He was arrested at the age of 18 in 2004 after a $250,000 bounty was posted for the computer virus’ creator. A friend of Jaschan’s tipped authorities that the youth had penned not only the Sasser worm but also the damaging Netsky.AC attack.
Jaschan was given a suspended sentence after it was found he was a minor when he wrote the malware. The Sasser worm crashed millions of PCs, and though some reports put damages at $18 billion, the relatively low infection rate suggests a more likely cost of $500 million.
Other notable viruses
The top 10 worst computer viruses above are just the ugly tip of a gargantuan digital iceberg. With a million new malware programs popping up every 3 years, we may miss the forest for a few outstanding trees. Here are just a few more viruses that have wreaked havoc over the years:
Mimail: This worm tried to harvest data from infected machines to launch a string of DDoS attacks, but was relatively easy to remove.
Yaha: Yet another worm with several variants, thought to be the result of a cyber-war between Pakistan and India.
Swen: Written in C++, the Swen computer worm disguised itself to look like a 2003 OS update. Its financial cost has been pegged at $10.4 billion, but not reliably.
Storm Worm: This worm showed up in 2007 and attacked millions of computers with an email about approaching bad weather.
Tanatos/Bugbear: A 2002 keylogger virus that targeted financial institutions and spread to 150 countries.
Sircam: A computer worm from 2001 that used counterfeit emails with the subject line, “I send you this file in order to have your advice.”
Explorezip: This worm used fake emails to spread to every machine on thousands of local networks.
Melissa: The most dangerous computer virus in 1999, Melissa sent copies of itself that looked like NSFW pics. The U.S. FBI estimated cleanup and repair costs at $80 million.
Flashback: A Mac-only virus, Flashback infected over 600,000 Macs in 2012 and even infected Apple’s home base in Cupertino, Calif. In 2020, there’s now more malware on Macs than on PCs.
Conficker: This 2009 virus still infects many legacy systems and could do significant damage if it ever activates.
Stuxnet: This worm is reported to have destroyed Iranian nuclear centrifuges by sending damaging instructions.
Error Causes for 0x80070002
A stop error or exception error commonly called the blue screen of death (BSoD) or blue screen, is an error screen displayed on Windows computers following a fatal system error. It indicates a system crash, in which the operating system has reached a condition where it can no longer operate safely. This is caused by many different problems, such as a general hardware failure or a crucial process terminating unexpectedly.
On Windows 10 systems, a Black Screen of Death can be caused by an unfinished Windows Update. To resolve this problem, simply hold the power button down on your PC or laptop to switch off the computer. A cold start should result in the system booting properly.
It is a diagnostic screen with a white type on a pink background. Pink Screen is mainly seen when the VMkernel of an ESX/ESXi host experiences a critical error, becomes inoperative, and terminates any virtual machines that are running. It is not fatal and generally considered more of a developer testing issue. When encountered, it can be fixed quickly by following the simple action of pressing and holding your computer’s power button to shut down the device.
The Microsoft Windows 10 Operating System Brown Screen of Death is an on-screen fatal error notification with bug check codes which is seen when a computer crashes due to graphics hardware or software-related problems (failing graphics drivers).
It affects the functioning of a browser, particularly Mozilla Firefox. The Yellow Screen of Death makes the appearance with a weird buzzing sound in the background when the XML parser refuses to process an XML document causing a parsing error and a weird buzzing sound. The issue persists unless the computer is manually rebooted.
Commonly the Windows 10 red screen is caused due to the hardware error, particularly if you overclock your Windows PC/laptop. Despite this, sometimes the red screen of death is also caused by outdated or incompatible drivers or due to BIOS issues.
The Orange Screen of Death on Windows occurs due to fatal hardware errors. Multiple reasons have been reported for the Orange Screen of Death. Some had this issue when watching a YouTube video, some were not able to boot into Windows. It can even occur when waking up from Sleep.
The green screen of death only appears when you're running an Insider Preview version of Windows 10. It's the same as the blue screen of death, and it will show the same error messages. ... If you see a green screen of death (GSOD) on your PC, that's a sign you're using an Insider Preview build of Windows 10.
The White Screen on Windows is also an error where the screen of the computer just turns white and freezes. There can be several things that can cause the white screen to appear on the Windows laptop monitor. But the main issue could be because of malfunctioning of the graphics hardware. 
For anyone who is not aware, when Windows 11 was released if you wanted to switch to another browser you had to go into the settings app and choose the default browser for different types of file extensions like HTML, HTM, PDF for opening on the web, etc. Of course, this was completely unnecessary and it was not well received by users. So after some time, Microsoft backpedaled to standard one click, choose your default browser solution that existed in the previous version of Windows OS.
Altho sometimes Microsoft knows how to irritate its users base, it is good to know that they can also listen and fix things that are required. Error code 0xC004E003 almost always appears when there are damaged files in the Windows operating system. These files could be corrupt for a number of reasons and are usually a serious danger to the life of the computer system. These file errors may be caused by a number of things. Incomplete installation setup, incorrect deletion of hardware or utilities, or an unfinished file erasure. The trigger might also be in the event that the computer system is contaminated with a virus or adware or spyware, or even by the improper shut down of the computer. Any of these scenarios have the possibility to result in the removal or corruption of data of the Windows system data files.
The data system files that are damaged will give linked data and archives that are missing or wrongly linked. These are needed for the proper functioning of the software. This can also happen when or after installing third-party software that might have changed the system files. If it is suspected that a program installation will need to be stopped, it is best to let it run through the setup and then delete it later. While it installs, it is altering program files, and likely rearranging them. Stopping this in the middle can scramble files associated with the program and files vital to the usage of the computer.
Error CausesThis error will pop up after installing third-party software that has changed the system files. These system files are necessary to finish the activation process. A restore point will be necessary if it is ultimately determined that a system restore is necessary, to bring the computer back to the state it was in previous to the failed installation.
There are several steps that can be taken when the error code 0xC004E003 appears. It is helpful to know that this can occur from trying to install third party software. Going forward, do not attempt to install third-party software that is not trusted, and does not attempt to abruptly stop the third-party software from installing. This may cause the program to corrupt the files or delete important files. Recovering from this error can be easy if there is a recent restore point already backed up in the recovery portion of the system's files.
Run an error scan. The problem should be resolved after rebooting the computer once these steps have been completed.
Best when utilized by an expert.
Another option for restoring. This method can be used by a novice.
NOTE: If there are no restore points available, the system recovery may not be turned on. To check this, go to Control Panel, and select Recovery. Configure System Restore, Configure. Then, select Turn on system protection. Having a current restore point for a computer ensures the ease of recovery if any problems with the computer arise.
If you wish to always have at your disposal a utility tool to fix these Windows 10 and other related issues when they do arise, download and install a powerful automated tool.
YourTemplateFinder is a browser extension developed by Mindspark for Google Chrome. This extension allows users to browse and download various templates that can be used for all kinds of occasions.
When installed, it changes your default search engine and home page to MyWay.com. During your browsing sessions, YourTemplateFinder will monitor user activity, recording website visits, user information, product purchases, etc. This data is later used to target better ads to users.
While browsing the internet with this extension active you will see additional ads displayed throughout your browsing sessions. Sponsored content such as links, banners, and pop-up ads will appear on websites sometimes even covering the website content.
This extension has been marked for removal by several anti-virus applications and has been classified as a Browser Hijacker due to its aggressive behavior and ad injections. It is flagged for optional removal.
