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Here Are 6 of the Most Pernicious Computer Viruses and Malware

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In one way or another, we’ve all been a target of computer viruses.

From being a mild inconvenience that requires a thorough cleanup, to becoming a costly damage for your device, viruses have been a bane for us all.

Malware like worms and Trojans have also contributed enough to our distress.

While most of them were quickly forgotten, the worst ones in history are still on our minds. We present you a list of the most notorious viruses (and malware) that have caused significant damage in the past.


Don’t fall for it… This is one of the most virulent software ever created! It wreaked havoc on systems around the world.

It was spread through an email attachment- a love confession! It’s not hard to see how it quickly spread from system to system, causing around $10 billion in damages.

Almost 10% of computers were infected by the viruses. Governments and top enterprises even took their office mailing systems offline to protect against attacks.

2. Code Red

Created in 2001, Code Red was a worm that only targeted computers which had Microsoft IIS web server installed. It hardly leaves any trace on the hard disk, as it mostly runs on the memory.

After infecting the system, it duplicated itself to make over hundreds of copies, eating most of the systems resources. Then, it launched a DDoS attack on several IPs and allowed backdoor access to the infected servers.

3. Sasser

Sasser is a Windows worm that was created in 2004. It affected millions of systems and resulted in disruption of critical infrastructure.

Taking advantage of vulnerability in Local Security Authority Subsystem Service (LSASS), Sasser caused computer crashes. It also used up resources for self-propagation and infected other machines too. This cost around $18 billion in damages.

4. Melissa

Another virus in the list, Melissa started as an infected Word document. It grabbed attention by claiming to have a list of password for various pornographic sites.

Curious, people opened the email which downloaded the virus. Next, the virus mailed itself to top 50 email IDs from the user’s email address book.

The result was increased email traffic and disrupted services at government and corporate offices.

5. CryptoLocker

A Trojan ransomware targeting Windows computers used multiple methods to spread itself. Once infected, the Trojan encrypted certain files on the hard disk and storage drive with RSA public key cryptography.

Affected individuals could only unlock files by paying a ransom within a set deadline. Law enforcement agencies finally put an end to it, revealing an estimated 500,000 infections overall.

6. Flashback

It’s not as harmful as others in this list, but the reason we’re including it is because it is one of the very few successful Mac malware. Flashback and others showed that Mac is not immune to malware.

The malware propagates through compromised websites with JavaScript code. This allows it to install on Mac systems and infect them.

Some of these viruses and malware are still out in the wild. Knowing that, protecting your system with a reliable online antivirus tech support is a better option. Contact us today for 24/7 virus and malware removal services.

Visit our website, call our toll free number +1 (240) 775-8797, or simply write to us at

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