What is a computer worm?


Computer worms are dangerous files that move through the internet. Learn more about how antivirus software can help prevent them.

While many of the headlines are given to ransomware, computer worms can be just as devastating.

Sure, the idea of a ‘worm’ doesn’t sound so scary, but they’re a serious threat if you’re not careful.

Worms have been around for decades and in the early days of the internet, they were responsible for some of the biggest hacks in history, causing billions in damage.

While ransomware rather loudly announces itself (you need to know you’ve been hacked to cough up the ransom, after all), worms are much more subtle.

You might not even know that you have one slithering around in your system.

So what is a computer worm?

A computer worm is a type of malicious software that travels through network connections all over the world to find its targets.

Worms are so dangerous because they exploit known computer vulnerabilities (for example, a problem in a computer’s security system) to get inside a machine. Once it’s in there, it’s really hard to stop as it travels far and wide to find its target.

Computer worms differ from computer viruses or other forms of malware in a couple of different ways:

  • It doesn’t target individuals, but rather any device it can find.
  • It isn’t sent directly to someone and doesn’t need to be opened or attached to a file to have an impact on a computer.
  • It’s main objective is to move as far as possible, not to cause direct harm.
  • It’s self-sufficient and moves across the world on its own.

Computer worms are dangerous despite the fact they aren’t necessarily associated with other common hacking techniques like stealing information – though they can be.

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How a computer worm works

The first computer worm, the Morris worm, was sent out into the world in 1988 and serves as a good example of how a worm functions. It was created as an experiment to see how far it could spread on the internet. In the end, it crashed around 10 percent of it.

The Morris worm crashed those operating systems because it consumes a large amount of bandwidth – or the speed that powers the internet – while it moves around. So, even though it didn’t carry anything particularly harmful with it like a virus, it was damaging because it made the machines useless until the file was removed from the system.

While worms spread on their own, they always have a point of entry, for example emails, free programmes downloaded from the internet (especially through peer-to-peer networks) and instant messaging services.

Most computer worms will slow your machine down, while others have evolved to cause damage, for example:

  • Dropping ransomware which locks your files until you pay a ransom.
  • Leaving behind malware that deletes the entire operating system or other parts of your computer.
  • Importing a keylogger, a programme that records everything you type, including account usernames and passwords.

Unless you have security software installed, you may not immediately recognise that a computer worm is in your computer.

However, there are certain red flags that could mean you’ve been infected with a worm:

  • Your computer is slower and freezes or needs to be restarted more often than usual.
  • Websites and the internet in general take considerably longer to open.
  • Someone who isn’t you is trying to get into your account.
  • Your email account is sending messages to contacts that you definitely haven’t written.
  • Files are missing or locked and you don’t know the password to them.
  • You’re getting warnings from your computer, likely from your firewall.
  • Applications and programmes opening without you clicking anything.

How to protect your computer from a computer worm

Protecting your computer from a worm is much easier than preventing a virus or other type of malware from making its way onto the machine. Here are the three things you need to do:

  • Always keep your security software running at all times. Not having an antivirus programme installed is like inviting a worm in. 
  • Never turn off your firewalls. Firewalls are an excellent defence against anything bad that’s sent through network connections on the internet.
  • Constantly update your computer. Computer vendors do a great job of issuing patches to help keep users safe. Even though updating your computer can be a pain at the time, always take a few minutes to download and install them. 

If you believe your computer already has a worm, take it to a local technical specialist or call the manufacturer’s customer support. A security suite can potentially help you figure out what type of worm it is and it will certainly go a long way towards helping keep your device secure in the first place.

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Editorial note: Our articles provide educational information for you. Our offerings may not cover or protect against every type of crime, fraud, or threat we write about. Our goal is to increase awareness about Cyber Safety. Please review complete Terms during enrollment or setup. Remember that no one can prevent all identity theft or cybercrime, and that LifeLock does not monitor all transactions at all businesses. The Norton and LifeLock brands are part of Gen Digital Inc. 


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