Your computer is in danger from viruses, worms, Trojans, hackers, etc. every time that you connect to the Internet to surf the Web or even just to simply pick up your emails. It is up to you to protect your system again such pests and attack; no one else is going to do it for you.
In addition to the above mentioned there are also adware & spyware, browser hijacks, and such lurking out there.
However, to help a little as regards to this matter this particular part of O DROM is intended. There are methods against many, if not indeed all, such pests. It is true that the writer of viruses, worms and such are getting more and more sophisticated and the same can be said for hackers. But it is possible to take measures of protection and you sure should do that. Not only because you do not want to loose your information and work stored on your computer but also so that you do not become a source to infect other computers by sending mail.
Another nearly as damaging thing, however, as viruses themselves are virus hoaxes (and other email hoaxes) where people are being asked to forward that "important information" to all on contacts in their address book. What happens when all those people send out emails to their friends and contacts in a mistaken sense of duty is that the system clogs up and can actually be brought to its knees. Always first check with reputable Internet sources as to whether this may be a hoax. I do. There is for one "Truth or Fiction.com" where you can check the validity or not of any such email that you receive.
Viruses: Most, if not indeed all, viruses arrive at a computer via an email attachment and this can even be coming from a person that you trust - or appear to be coming from a person you trust. Therefore the best advice is not to open email attachments. I personally have a message on the bottom of my emails (part of my electronic signature) that states "Anti-Virus Note: I do NOT open email attachments". That puts people on notice that - unless I have been previously informed that a safe attachment is being sent to me - I will not open any attachment and in fact I do delete any message with attachment. If you use Outlook Express (I do not know about Outlook, as I do not use it or other email clients like Eudora or Bat) to receive emails onto your PC then it is possible to set Outlook Express' security setting in such a way as to have the program disable automatically all email attachments with the exception of .doc files. Any pictures sent to you are automatically put safe into the body of the email and you can save them from there into your picture folder should you wish to do so. To do this open Outlook Express, click on "Tools" and then "Options". When the box opens with all the tabs on the top click the "Security" tab and under "Virus Protection" set "Restricted sites zone", tick "Warn me other applications try to send mail as me" and then tick the most important one, the one underneath the one previously ticked, that says "Do not allow attachments to be saved or opened that could potentially be a virus". Now that is for starters. On top of that you need to get a good, reliable anti-virus program. There are many on the market but most of them cost money and many quite a bit. But it does not have to cost any money at all and still you can get one of the best systems on the market - according to the reviews carried out by many computer magazines - and that is AVG6 from grisoft.com. The FREE version is all you need and it has regular updates and I have been running it for a considerable time already and love it. However, it will take 2 hours or more to download with a 56k modem on dial-up.
Worms: Worms arrive basically the same way, as do viruses, that is to say, via email, but can also arrive via other sources. Even by simply visiting a website that is "infected" or being used as a "carrier" a worm (as it happened, apparently with the "Blaster worm") can get into your system if you have no protection. In the latter case you do not just need anti-virus software but a firewall.
A firewall also is the protection needed against hackers. Again you can go and buy a firewall program but that is not necessary yet again as a good but free one is out there that is adequate enough for the ordinary user (theoretically the FREE version may only be used on personal private PCs) and that one is Zonealarm. The free version does not have all the facilities that the Pro version, the one you have to pay for has, such as tracking the IPs of anyone attempting to hack your system but then, do you really need that? The way to run Zonealarm is in the "stealth mode" and that is the way that is safest for you.
So, as you can see, you do not have to spend a small fortune on protection software for your PC; it can all be had for the download or as cover CDs from magazines - at least in countries like the UK.
Hackers: Against hackers there is only one protection and that is a good firewall, like Zonealarm (free version will suffice), and running that on the highest setting that still permits you to access websites.
Adware & Spyware: What is that, you ask. Both are components that have a similar function and I could, probably, write a complete section on that alone, Suffice to say, you do not want that on you system. It infringes you privacy and security. Many free programs that you download from the Net, be this games, toolbars, etc. have one little drawback and that is adware and worse, spyware. Those come in the form of "cookies" but also complete folders and even registry entries. Now those you certainly do not want because this is "ET calling home". In other words, those things report back to source while you are surfing the Net as to where you go, what you look at and so on but worst of all they may also pass on other information stored on your computer. So, the answer is finding those things and eliminating them. For that yet another program is needed. But don't worry! Help is at hand in the form of "AdAware" from Lavasoft.com in Sweden. Again this program is FREE and it catches all them little nasties that many spyblocker programs even miss. Run this program every time that you have finished surfing the Net and your system should remain clean. Once you have downloaded "AdAware" and have run the scan for the first time you may be rather surprised how much spyware you have already accumulated on your system that you did not know was there. Some of the "data miner" cookies that turn up virtually daily from various sites that you visit are rather harmless but they should, nevertheless, also be removed with all the rest that "AdAware" finds.
Please keep an eye open for download links for the programs that I have mentioned and for others that I/we may come across.