The internet presents many opportunities for con-artists and fraudsters. Internet security experts Messagelabs have been examining the threats of the past year.
Here is a guide to the biggest threats to your computer's security.
Nasty little programs that can wreck your system or take control of your computer, viruses are still a growing threat.
In 2004, one in 16 e-mails was infected - that is 6%. The biggest offender of the year was the MyDoom "A" virus.
This, like a lot of malware, opens a backdoor in your computer system, allowing any program to be downloaded and run on your machine.
We are also seeing a shift in the motives of viruses writers.
Some, seduced by dirty money, are trying to take control of your PC and sell its resources to organised crime.
What on earth can they want with your computer? They want to make it part of a network of zombie PCs, used to distribute this:
We all know about spam - we all get inboxes full of it! Unsolicited junk e-mail is still on the increase.
Over the last three years we have seen the amount of spam flying around the 'net grow at phenomenal rate.
9% of all emails were identified as spam in 2002. A year later that had risen to 40%. And last year, a mailbox-busting 73% of all e-mail was spam - that is 9.2 billion junk messages!
What do you think most spam is about? Unsurprisingly, most of it is trying to sell us something.
Spam is becoming more and more pervasive
Matt Sergeant, of Messagelabs, says: "The vast majority of spam is sent from 200 or so spammers, most of them based in the US.
"They're trying to sell you pornographic material, cheap watches, that sort of thing.
"While we see the e-mails coming from various countries around the world such as China, Brazil, England, home PCs located everywhere, all of the money is actually going back to the US despite where the emails are coming from."
But there is some hope. New anti-spam laws and some high-profile spammer arrests could see these figures plateauing and even starting to come down.
But this could also mean that spammers will simply move their operations into countries with weaker regulation, like Russia or China.
Apart from being a nuisance and hogging storage space, most spam is relatively harmless. Some, however, is far more destructive.
The most sophisticated of the bunch, phishing e-mails, pose as official e-mails from banks and other institutions.
They ask you to click on a link, which takes you to the bank's official website... or at least something that looks like the official website.
It is actually a fake, and the bank details and password you enter into the phoney logon screen is actually sent straight to the scammers.
After a gradual increase in phishing e-mails that were intercepted up to June last year, there was a sudden explosion. In July, there was a ten-fold increase.
Over the last few months phishing, and its ability to steal your online identity, has become the principal online threat.
Matt Sergeant: "Spammers use images in their e-mails as a way to avoid text-based filters that are looking for particular words or phrases in the e-mail.
"By using images you can't pull out the words in the e-mail so you can't see that the spammer is trying to send you off to Paypal or Citibank."
Four million phishing e-mails are now intercepted every month, and the amount that goes unreported is thought to be much higher.
So what will 2005 bring forth? Will these security threats continue to grow?
We spoke to Nigel Beighton from security experts Symantec, and Bryan Glick, the Managing Editor of Computing Magazine.
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