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.
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.
Most of the time running applications with typical settings is fine but from time to time we might have some applications that will require running with administrator privilege in order to work properly. In this case, it is very easy to do it, you just right-click and choose run as administrator.
Although a very easy solution, it can be quite annoying if running the app is on a daily basis or even more times per day. If this is the case then right-clicking and choosing to run as administrator can be a daunting task, sometimes you can even forget to run it like this in heat of work and some unforeseen consequences might occur.
Luckily there is an easy hack so you can open the chosen application each time as an administrator with a simple double click each time.
This error is quite common and is faced by many Microsoft Outlook users. It is advisable to fix this error immediately because besides restricting you from sending and receiving emails via Outlook, due to this error the data on your Outlook also becomes inaccessible and unreadable, and sometimes Outlook also begins to freeze unexpectedly.‘Receiving reported error (0x800ccc92): Your email server rejected your login.’
chkdsk C: /f /x /rNote: “C” is the drive root drive so it could be changed if you’re using a different one.
Blackouts are one of the most annoying things that can happen in the modern age. We have all learned to depend on electricity, maybe too much, so having a backup plan in these unpleasant situations is necessary. Here are some good gadgets for these kinds of situations.
The fully charged power bank is a great item that could fill up your phone or tablet. If it is a larger power bank it could fill them up all the way to the top several times and having charged phone or tablet can help greatly with some fun during dark times. The power bank can also be used to fill up other gadgets on this list so if the power outage is expected to last longer perhaps it would be wiser not to waste it on phone/tablet games.
If the power bank is too short-lived for your needs, a portable generator is always a good option since it can provide power for longer time periods. The solar generator is what we recommend because it is much cheaper to produce electricity but it is limited if a power surge comes at night, one on gasoline is more stable and practical but it costs more to produce electricity.
One more electric-producing device on the list, this one however is aimed at charging your phone, tablet, or laptop by harvesting Sun's energy and turning it into valuable electricity for your devices. Fully silent and easy to operate this is a great tool for power outrage. It will not be able to produce electricity for smaller house appliances but for basic phone/tablet/laptop needs it will suffice.
Self-sustained with its own battery, panic lights are great assets for lightning when power is not present. They can turn automatically when the circuit detects that power is missing but can be also manually switched on or off. There are many versions of panic lights ranging from the light they produce to how long can they work so picking the right one will depend entirely on your home size and needs.
If you lack panic lights USB headlamp is a great choice to light your way and it works even better than a flashlight, although a flashlight is also a great tool, a headlight will provide you with free arms to do various things that you would not be able to by holding a flashlight. Modern headlights come with LED lights so they provide a good amount of light with small power consumption and they can be recharged in a power bank, solar charger, or generator.
LED Lantern is a gadget sitting somewhere between a headlight and a panic light, it offers around the same light amount as a panic light but you can carry it around with you. Of course, it will drain its battery faster than a panic light and it will still need to carry around but it can offer some good options when you need it, like taking it with you to the toilet.
An electric lighter is also one of the things that you will need, it can ignite candles, paper, stoves, etc. Its battery is usually enough for extensive use and there are small chances that it will need to be recharged. Having matches is also smart, just in case.
Great gadget when outbreaks last long or when you get hungry. Not all households have gas ovens so a Solar oven is a great tool to keep you full of food. Granted it will not be on par in speed and quality with a regular oven but when it is the only option it will suffice.
I do not know about you, but I prefer to set my Windows to be more to my liking and not how Microsoft thinks it should be. Let’s face it, not all users feel comfortable whit Microsoft settings and idea how things should be.
One of the things I particularly did not like even in Windows 10 is icons that come by default on my taskbar, now so far, well until the latest Windows 11 update you could remove default taskbar icons the same way as in Windows 10, just right-click on them and unpin, sadly with latest update build on Windows 11 this option has been removed.
In order to remove default icons from the taskbar, one must go now to Windows 11 settings and choose from there which one you would like to be placed on it. Of course, this is nothing game-breaking but it still feels strange why the standard option has been removed, it just makes no sense but lately not many things that come from Microsoft do.
I do not know about you, but I prefer to set my Windows to be more to my liking and not how Microsoft thinks it should be. Let’s face it, not all users feel comfortable whit Microsoft settings and idea how things should be.
One of the things I particularly did not like even in Windows 10 is icons that come by default on my taskbar, now so far, well until the latest Windows 11 update you could remove default taskbar icons the same way as in Windows 10, just right-click on them and unpin, sadly with latest update build on Windows 11 this option has been removed.
In order to remove default icons from the taskbar, one must go now to Windows 11 settings and choose from there which one you would like to be placed on it. Of course, this is nothing game-breaking but it still feels strange why the standard option has been removed, it just makes no sense but lately not many things that come from Microsoft do. 
Mapping network drive has many benefits in terms of speed and ease of access of files via network. It lets you access the hard drive over the whole network like it was the hard drive inside your PC case. In order to easily and quickly map a folder as a network drive follow the guide below.
