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.
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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.
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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.
If the Error Code 0xC004C770 popped up on your computer during your activation of the Windows 10 software, don’t worry. This is a fairly common error, especially for people who own more than one computer upon which Windows 10 is installed and activated. The gist of this error code is that the product key that you have entered has already been claimed or used on a different computer. Because there are limitations on the number of computers that can use any given license activation code or product key, this error code can arise when you have exceeded that limit. If you have a single-use license and have already entered the particular product key onto another machine, you may see this error come up during activation.
Both Error Code 0xC004C770 and Error Code 0x803FA071 arise from the same problem and the same steps can be used to resolve both error codes.
Error CausesError Code 0xC004C770 is likely to appear on your screen during activation of Windows 10 if you or anyone else in your organization have already entered in the product key used on another computer. If you have a multiple-use license, the product key that you are entering may already have been used for the maximum number of computers allowed under that license.
There are two basic methods for addressing the issues associated with Error Code 0xC004C770. These methods can easily be implemented by anyone who is comfortable interacting with the Windows Store from their computer, which makes the resolution of this particular error code fairly simple and straightforward.
If you are unable to complete the steps below or Error Code 0xC004C770 has not been resolved after following the guides below, contact a Windows technician who is familiar with the Windows 10 activation process to assist you in the process. You can also get in touch with the Windows technical support team to assist you in the process if needed.
If you have already used the product key on another computer or have used it on the maximum number of allowed devices, you may need to purchase an additional product key for the computer with Error Code 0xC004C770. Product keys can be purchased physically from a retailer that sells Windows 10 software licenses or purchased directly from the Windows store.
To purchase a new product key directly from the Windows Store, follow the steps below:
If you are unable to see the “Go to Store” option when you reach the “Activation” page, you may not be set as an administrator of your machine. In this case, get in touch with the support personnel from your company to complete the purchase, installation, and activation process on your computer.
For users who have changed out parts of their computer’s hardware, like putting in a new motherboard or activating a new hard drive, you may have more success if you attempt activation through a phone.
In order to activate your copy of Windows 10 from your phone, follow the steps below:
As with any error code resolution, if the methods above are not successful or if you are not comfortable with your ability to successfully complete the steps above, get in contact with a qualified professional who is trained in the Windows 10 activation process to assist you or download a powerful automated tool to get the job done.
“We couldn’t install Windows in the location you choose. Please check your media drive. Here’s more info about what happened: 0x80300002”You can encounter this kind of error if there is corruption in the partition table of the drive where the installation is in progress. In addition, corruption on the Media device could also cause this problem. So if you encounter this error when running Windows Setup, read on as this post will guide you in fixing it. There are several ways to resolve this issue. The first thing you can do is to verify the compatibility between the BIOS and the installation media. You could also try recreating all the partitions as well as recreating the bootable USB drive. For more detailed information, follow the given options below.
The program can’t start because MSVCR71.dll is missing from your computer, Try reinstalling the program to fix this problem.If by any chance you have encountered this error know that you are not alone and that this is a solvable error. In this guide, we will show you how to fix this error. Usually, the MSVCR71.dll missing error is met when a new application is installed. So let us dive right into it and solve it.
del /f %windir%logscbs*.log
MovieMode is a Potentially Unwanted Program developed by GenTechnologies Apps that allegedly ads a “Lights Off” function to video streaming websites like Youtube. This feature allows a user to dim the entire background around the video, allowing for better video focus. Although this sounds interesting and useful, upon further inspection it was discovered that this program does not work with modern browsers.
While installed, MovieMode may modify your browser settings, changing your home page, displaying additional ads, and other suspicious behavior. From the Terms Of Use: “Applications may be automatically enabled on your web browsers following installation. Applications or advertisements may require changing your web browser’s default home page, default page, or set of pages on startup, default search provider, and other browser settings. So that Applications can function most efficiently and with the least annoyance, Applications may modify or disable certain web browser or operating system features including, but limited to load time alerts, accelerator features, and Content Security Policy functionality. Applications may also include features to notify you when you are launching an application or visiting a web domain that may interfere with your installed Applications. “0xC1900101 – 0x20017, The installation failed in the SAFE_OS phase error during Replicate_OC operationTo fix this issue, you need to follow the given options below. But before you do, you need to create a System Restore point first so that if anything goes wrong, you can always undo the changes you’ve made.
dism /Mount-Image /ImageFile:H:sourcesboot.wim /index:1 /MountDir:C:UsersUserDesktopmount
C:UsersUserDesktopmountWindowsSystem32mcupdate_GenuineIntel.dll
dism /Unmount-Image /MountDir:C:UsersUserDesktopmount /commit
