7 Most Catastrophic Computer Viruses of All Time

The 7 most catastrophic viruses of all time are truly a sight to behold because even though they have wreaked havoc on whatever their intended targets were, they managed to do so in an unpredictable and unstoppable way that is worthy of respect. Coming from the list of the most common online threats you should know about, you should be pretty well informed on just how desperately some people or communities are to harm you through your web surfing habits.

Let’s take a look at what a computer virus is by definition (for the uninitiated). One of the simpler ways to describe it is by calling it a piece of computer code which can and likely will replicate (pivot) itself to other systems, that aims to corrupt or destroy data. Viruses come in many sizes and shapes and there are many categories of malicious code which many consider subclasses of the computer virus and other consider them categories of their own. You will see a lot of different lingo like “worm”, “trojan horse” and the likes which signify the different means of infection and propagation that malicious code could use. There are also threats which combine all the worst aspects of every single subclass of a virus you can imagine. There are Remote Administration Tools (RATs) which come packaged with malicious code that allow an attacker to basically take full control of your computer and its peripherals, including looking through your webcam, listening to your microphone, seeing your screen and looking at everything you type.

There are more people who are trying to get you to fall into a trap than there are people protecting you from them out there. Of course, if you are a simple individual and not a government agency or a company, you aren’t at much of a severe threat from a complex attack you could do nothing about. Getting infected with a virus will always include you opening a file of some sorts, which today can include anything from pictures (.PNG) to documents (.doc/docx, .pdf) but mostly come in .exe files which are completely obvious to anyone with more than two days of online experience. There is seldom a way for a virus to find its way into your system on its own, you will often have to let it do it yourself. From then on, however, it will find a way to propagate. Let’s take a look at some of the most destructive such pieces of code – the 7 most catastrophic computer viruses of all time.

7. Sasser

Estimated Damage: $500 million

The Sasser was written by a 17 year old German student, who upon his 18th birthday released this beast of a worm in the wild, where it spread like wildfire. Its main destructive force was its way of quickly finding new vulnerable machines on the network of each new infected one and spreading through, shutting down thousands of networks.

6. Melissa

Estimated Damage: $1.2 billion

The Melissa virus was a Microsoft Word macro virus which spread as a .doc file that was mass-emailed as a document full of adult website passwords (which at the time were precious). The virus, once activated, caused a globally noticeable slowdown in internet browsing because of the sheer speed of spreading it had.

5. Code Red

Estimated Damage: $2 billion

Code Red, named after what its discoverers were drinking at the time of their discovery, was a virus which targeted computers running a specific service. Once infected, they would display a message saying “Welcome to www.worm.com / Hacked by Chinese!” in their web browsers and after two weeks, all infected computers were programmed to launch a DDoS attack on major websites.

4. Conficker

Estimated Damage: $9.1 billion

Lovingly named Conficker, a combination between configure and a censoring-worthy German word, this virus cause billions of damage by doing nothing on its own but downloading more malware from predefined sites. The virus was first sighted back in 2007.

3. ILOVEYOU

Estimated Damage: $15 billion

This affectionate piece of malware is one of the most virulent pieces of code in the history of the world wide web. It started out as an email attachment masked as a love message in a text file. While its creator claims that it was released accidentally, the virus spread globally in a day, going as far as infecting Pentagon machines. It is also the reason for the creation of laws against viruses.

2. SoBig.F

Estimated Damage: $35 billion

SoBig.F is another mass mailer which spread through millions upon millions of systems, stalling and crashing servers of all kinds and effectively slowing down global internet speeds. However, the virus was programmed to deactivate itself in September of 2003(the year it was released) after which it ceased to exist,

1. MyDoom

Estimated Damage: $38 billion

The king of the 7 most catastrophic computer viruses of all time is MyDoom, and there are no two different opinions about it. It did no malicious changes to the infected machines. Instead it spread at such a mind-boggling speed, that it slowed down global traffic by at least ten percent and caused billions of clean-up costs.