Security Centre


What do I need to know? : Malicious software

What is it?

Malicious software or malware is an umbrella term for a number of different types of programmes that have been designed to infiltrate or damage a computer without the owner's informed consent.

The damage malware can cause depends on the specific malware and includes simply slowing your computer down, sending sensitive data (such as credit card details) to its creators and, destroying computer files.

There are a number of different types of malware:

A virus is a programme designed to reproduce itself by “infecting” other programmes with copies of itself. They can only be transferred by running an infected programme on an uninfected computer where it will find  clean files to infect. Originally they were transferred from one computer to another by infected programmes on floppy disks, however today they are most commonly transferred through infected programmes sent via e-mail. Besides infecting other files, a virus may be designed to specifically damage your computer in other ways.
Worms are similar to viruses, but where viruses infect programmes, worms infect computers over networks, without the need for a user to run an infected file. One of the dangers from a worm is that they can slow down or even incapacitate an entire network as more and more infected computers repeatedly send out thousands of copies of the worm. Some worms install “backdoors” that allow hackers to take control of infected computers.
Trojan horses
Like the mythical wooden horse used to trick the Trojans into letting the Greeks into their fortress, a trojan horse is malicious software that appears to be useful or entertaining software, but will do some form of damage when run. For instance, a trojan horse may install a virus or a “backdoor” programme to allow hackers entry to the computer it is run on.
Spyware spies on you – and sends information it gathers about you back to its creators without your knowledge or consent. Besides sharing sensitive information about you without your consent, spyware may cause your computer to slow down and may use up your bandwidth.

Why do people create these things?

They could be seeking recognition, or they could be trying to steal data, or they may want to sabotage someone’s computer out of spite or for financial gain.

What can I do?

Most importantly keep your computer up to date, visit Windows Update once every two weeks and install the latest updates.

A lot of malware is sent via e-mail. MWEB’s e-mail Virus Filtering will automatically clean any e-mail sent to you of any malware it recognises. However you should still be careful and scan any programmes you receive over e-mail, even if they come from someone you know.

Any programmes you have downloaded off the Internet or received on a CD should also first be scanned, even if they come from a reputable source.
To scan for viruses use an up-to-date virus scanner, such as the one provided with AVG.

You should also run an up-to-date anti-spyware programme, such as the one provided with AVG, at least once a week to make sure your system is clear of spyware.

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