List of all known computer viruses

Very few worms managed to infect so many computers and do so much damage — nine billion USD. The virus used a vulnerability in a Windows network service that Microsoft took too long to patch. The active infection reset account lockout practices, blocked the Windows update and antivirus websites, turned off the services that could identify it, and locked out specific user accounts. Once all those changes are affected, the worm downloads and installs another piece of software that turns the computer into a slave in a botnet.

Here are a few more worthy mentions extending the legacy of the worst computer viruses:. The difference between a virus and a worm is very straightforward to understand. A virus is a parasitic code that needs another program to activate it or make it work. On the other hand, a worm can run without any help. Viruses and worms get into systems in many ways. For instance, the most frequent method of getting infections right now is to click on attachments, open files, or follow link s in unwanted emails.

How is that possible? Because many a virus will impersonate somebody else to persuade you to open that link or launch that file. But, since not every virus works the same way, you cannot generalize how your computer should act upon getting a virus.

Nonetheless, you can certainly avoid a few careless habits that often lead to virus infections on your computer, phone, or any other device. Do you have an email from AppleSupport gmail. Likewise, be paranoid about attachments. Your late distant granny would have preferred contacting you directly instead of asking somebody else to hand over her remaining property to you. Not every email you receive is legit.

Today, digital advertising is the bane of computer security. This is because a lot of malware spreads through ads on malicious websites. You can prevent this risk by avoiding fishy sites. But, of course, not all the ads in the world are dangerous. Or you could adopt a more active measure. For example, some VPN services can block ads.

Likewise, you can use the more dedicated tools — the adblockers — for this purpose. While free WiFi hotspots are an attractive marketing strategy from hotels and other public places, they are seldom secure. Often, these public WiFi harbor cybercriminals who keep looking for victims to infect their devices and steal data.

Unless you have a robust antivirus and a VPN on your device, avoid connecting to such free WiFi to protect your online privacy and security. Just open your antivirus and see what it tells you. For example, Windows 10 has a Windows Security feature, which includes an impressive protection tool against viruses, the Windows Defender. You can even turn on its notifications to watch when and how it scans your system. The study of computer malware is not an established science at all.

In fact, much of it relies on artistic intuition, ironically. So how did we choose our top twelve entries for the most malicious computer viruses? We considered estimates of lost work, infection length, the estimated number of infections. Also, cleaning up a virus takes resources, and we considered that too. The truth is that nobody has any accurate data. Still, we considered several reports and shared with you something that was somehow common among the various sources.

The world spends at least 55 billion USD cleaning up and repairing the damage that results from the spread of viruses and worms. Mydoom has the record for damage, at 38 billion, but there have been many other strong hits. However, the future looks bright regarding malware and virus prevention measures. Just keep your system updated at all times, get a good antivirus suite, and apply cybersecurity best practices to stay safe online.

Above all, remain aware. Keep visiting our site to educate yourself on privacy, anonymity, and security issues so you can always keep yourself a step ahead of the rest. Stay safe. It was so bad that governments and large corporations took their mailing system offline to prevent infection. What it did was use social engineering to get people to click on the attachment ; in this case, a love confession. The attachment was actually a script that poses as a TXT file, due to Windows at the time hiding the actual extension of the file.

The two were never charged, as there were no laws about malware. This led to the enactment of the E-Commerce Law to address the problem. Code Red first surfaced on and was discovered by two eEye Digital Security employees. The worm targeted computers with Microsoft IIS web server installed , exploiting a buffer overflow problem in the system. It leaves very little trace on the hard disk as it is able to run entirely on memory, with a size of 3, bytes.

Once infected, it will proceed to make a hundred copies of itself but due to a bug in the programming, it will duplicate even more and ends up eating a lot of the systems resources. It will then launch a denial of service attack on several IP address, famous among them was the attack on the White House website.

It also allows backdoor access to the server, allowing for remote access to the machine. The most memorable symptom is the message it leaves behind on affected web pages, "Hacked By Chinese! A total of million servers were affected, which is amazing when you consider there were 6 million IIS servers at the time. Named after an exotic dancer from Florida, it was created by David L.

Smith in It started as an infected Word document that was posted up on the alt. This got people curious and when it was downloaded and opened, it would trigger the macro inside and unleash its payload. It also sometimes corrupted documents by inserting a Simpsons reference into them. Smith was eventually caught when they traced the Word document to him. The worm allows its creators to remotely install software on infected machines. What will that software do? We don't know. Most likely the worm will be used to create a botnet that will be rented out to criminals who want to send SPAM, steal IDs and direct users to online scams and phishing sites.

Melissa -- Melissa was an exotic dancer, and David L. Smith was obsessed with her and also with writing viruses. The virus he named after Melissa and released to the world on March 26, , kicked off a period of high-profile threats that rocked the Internet between and Slammer -- This fast-moving worm managed to temporarily bring much of the Internet to its knees in January The threat was so aggressive that it was mistaken by some countries to be an organized attack against them.

Nimda -- A mass-mailing worm that uses multiple methods to spread itself, within 22 minutes, Nimda became the Internet's most widespread worm. Ransomware is a kind of malware that takes your files hostage. You know in heist movies when the bad guy grabs someone and threatens them in return for money? Ransomware works much like that, except your computer is taken hostage by a faceless bad guy.

The hackers then sent a decryption key in return for a sum of money , usually somewhere from a few hundred pounds up to a couple of grand. With some of the hacking attempts, System Restore or recovery software worked. Now is a good time to remind you to always back your files up! Well, in malware was a bit of a myth.

In fact, it was such a myth that malware could get away with being completely unsubtle. We hope! ILOVEYOU hit headlines around the world and still people clicked on the text—maybe to test if it really was as bad as it was supposed to be.

Poking the bear with a stick, to use a metaphor. A viral virus, by all accounts. Two young Filipino programmers, Reonel Ramones and Onel de Guzman, were named as the perps but because there were no laws against writing malware, their case was dropped and they went free.

MyDoom is considered to be the most damaging virus ever released—and with a name like MyDoom would you expect anything less? A version of the virus allegedly hit the SCO website with a boatload of traffic in an attempt to crash its servers. Who was Andy? Who knows. Storm Worm was a Trojan horse that infected computers, sometimes turning them into zombies or bots to continue the spread of the virus and to send a huge amount of spam mail.

By July , Storm Worm was picked up in more than million emails.