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| Viruses, Worms & Trojans - Part 1 |
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PC support #2: Viruses, Worms and Trojans, part 1
6th October 2001
C O N T E N T S
----- VIRUSES, WORMS AND TROJANS
1. What are Viruses, Worms and Trojans?
2. If I don't click on e-mail attachments, I'm safe, aren't I?
3. So how do they get onto my computer?
4. What do they do?
5. So how do I know if I've got one?
6. I've got a virus but it seems harmless. Can I leave it?
7. So what can I do to protect myself?
8. I've got an Anti-Virus program, so I'm safe, right?
----- CONTACT DETAILS
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----- VIRUSES, WORMS AND TROJANS ---------------------------------------
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-- 1. What are Viruses, Worms and Trojans?
Viruses, Worms and Trojans are programs which are written by malicious individuals and intended to interfere in some manner with the normal operation of the computers they infect.
The difference between a virus, a worm and a trojan is fairly subtle and outside the scope of this support note. For the rest of this note I will refer to them all as viruses for simplicity.
-- 2. If I don't click on e-mail attachments, I'm safe, aren't I?
I'm afraid not. One of the most common ways they spread is via e-mail attachments, but there are other methods that some use to spread (see below) and you can catch some just by reading an e-mail (e.g. the "KAK" worm).
-- 3. So how do they get onto my computer?
That varies from virus to virus. The most common method is via infected e-mails, particularly e-mail attachments (which could well come from someone you know - that doesn't guarantee it's safe!), but they can also spread in other ways. Some of the more common methods are:
* E-mail
* Web sites
* Files downloaded from the Internet
* Commercial CD ROMs - particularly free CDs
* Disks (Floppy, CD or other types) from other people
-- 4. What do they do?
This again varies widely. Some don't do much other than cause minor irritation (for example, occasional crashes or the odd program no longer working correctly) whilst others can cause major damage, deleting files from your hard disk and (in extreme circumstances) erasing the entire disk! However, whilst they will corrupt the information stored on the PC, they won't damage the PC itself.
(I have heard rumours of viruses which could damage the PC, and theoretically it might be possible, but it is very unlikely and I am not aware of any which are confirmed to be able to do this).
-- 5. So how do I know if I've got one?
It can be hard to tell without an anti-virus program (see below). There are various signs, some minor, some major. Some typical signs are: your computer connecting (or trying to connect) to the Internet at unexpected times; a lot of unexpected hard disk activity; strange messages or programs suddenly refusing to work; files getting corrupted so that you cannot open them; your PC slowing down.
However, all of these can be caused by other things as well, so don't be too quick to shout "Virus". You really need an anti-virus program (or a good knowledge of computers and viruses) to be sure.
-- 6. I've got a virus but it seems harmless. Can I leave it?
Please don't! For one thing, it may well cause more harm in the future (for example, some are "triggered" on certain dates). However, even if it doesn't, it's rather anti-social, as you are probably infecting other
people's computers with it (for example, via e-mail).
-- 7. So what can I do to protect myself?
For starters, install an anti-virus package. There are several available, and many newer PCs are shipped with one. Some of the most common are:
* Norton AntiVirus
* McAfee VirusScan
* Trend PC-Cillin
but there are also a number of others. Some are a bit better than others, but in the end they will all do the job, so it doesn't really matter which you choose. My current personal preference is Norton - it's not the cheapest (30 to 40 pounds) but it's easy to use and effective.
-- 8. I've got an Anti-Virus program, so I'm safe, right?
Not necessarily. There are several things you must do:
* Make sure it's running!
* Update it regularly
* Make sure it's configured correctly
* Scan your whole PC periodically
I'll cover these in more detail in my next support note.
Finally, you should not regard an anti-virus package as a total solution to all your virus problems. There are some other basic precautions you should follow, which I will also cover in another support note.
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----- CONTACT DETAILS -------------------------------------------------
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Chris Livingstone
e-mail: mailto:chris-l@ntlworld.com
web site: http://www.pcparamedic.org.uk |
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