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Today the term malware is commonly used to describe all different kinds of malicious software that can infect your computer to steal data, purposefully cause damage, or launch attackson other computers. A virus is a type of malware along with trojans, worms and spyware.

 

 

 

Worms are malicious programs that duplicate and distribute themselves using LAN's (local area networks) and the internet. Worms typically spread through emails, instant messaging, peer-to-peer file sharing programs and by exploiting security vulnerabilities in windows or other software running on your PC. Very often a worm will be desighed to conduct some malicious activity, such as deleting files on your Hard Drive.

Worms may also include so called 'back doors' which leave holes open on your computer for further infection by other malicious programs, or actively downloads other malicious programs from the internet to infect the host computer. The key difference between a virus and a worm is that a worm can propagate itself, whereas a virus requires some king of 'host' to transmit it.

 

 

A virus works by inserting itself into code of another program, so that it is run when the host program is executed. It spreads in a similar way to a biological virus, which inserts itself into living cells. Viruses can be destructive, or merely annoying, for example, by displaying a message on a certain date.

 

A virus can also use a document that can contain scripts as a host, such as word documents that use VBA (Visual Basic for Applications) saripts. A virus can replicate itself, commonly by copying itself on to a floppy disk in an infected system and then infecting any systems that the disk is inserted into. Nowadays the meaning of the term virus has become broader to cover much of the behaviour of worms.

 

 

By analogy with the story of the Trojan horse a Trojan in computing terminology is a malicious program that is disguised as something alse. While the program may have some usefull functions, it also has other secret, undesired, functions that the user dose not know about. The difference between a Trojan and a virus is that a Trojan dose not replicate itself, but instead fools a user running it by posing as something else.

 

 

Your computer may be infected with a virus without you even knowing about it. More likely there will be telltale signs you will see when using your PC that give a good indication that you are infected.

 

 

 Your PC is running much slower than usual, and normally quick programs are taking a long time to load.

 

You get email from friends about messages you have sent them, even thoughyou don't remember sending them email. This is because some viruses will spread by automatically emailing all of your contacts.

 

The Hard Drive is being accessed very frequently (indicated by the Hard Drive light on the front of the case)

 

Files or documents have mysteriously dissappeared from your Hard Drive.

 

Programs crash with strange error messages, or you get error messages appearing when you start Windows.

 

Your desktop background has been changed, possibly to an offensive message.

 

New icons have appeared on your desktop, and you have no idea where they have come from.

 

Adverts keep poping up on your desktop, especially when browsing the internet.

 

 

Do not open any files that are attached to an email that is from a suspicious, unknown or untrustworthy source.

 

Don't open files attached to emails even from close freinds or colleagues unless you know what they are. Be particularly wary of emails from people that you know with strange subject lines. Some viruses can automatically email themselves to everyone in the address book on an infected PC.

 

Backup you files on a regular basis.

 

Install anti-virus software on your PC and use it to scan your Hard Drive regularly. There are many different virus scanners, both free and commercial. some of the best will be listed at the bottom of the page.

 

Update your anti-virus software regularly. With over 500 new viruses discovered each month. Your anti-virus software is unable to block viruses if it dosn't know about them.

 

If you transfere data between computers using floppys or removable usb sticks, make sure you scan them with your virus checker as soon as you insert them into your PC.

 

Set your virus checker to scan all incoming emails before they are deliverd to your inbox.

 

The most important thing to remember when exploring the online world is to always err on the side of caution. If you recive an email promising something that is to good to be true it probably is, and clicking on a link in it may well infect your PC. Never download a file from the internet if you are not sure what it is or don't trust the source, and always be wary of programs sent to you via instant messaging applications.