There are many nasty viruses around looking to infect your PC. The most recent is the Conficker worm that has infected up to 15 million computers and because of today being April 1^st, it has been said it will cause havoc.

So what defenses do you need to protect yourself? There are at least 5 level of protection you need to keep the nasties at bay.

1. FireWall

This could be considered the first level of protection. To understand why you need a firewall lets take a look at what needs protecting.

Imagine your computer has lots doors. Each door opens to pass data to other computers and to receive data from them. In correct terms, the doors are called ports. Your web browser sends and receives data through port 80, when you send files to your website and website host with FTP (file transfer protocol), you use port 21.

There are many programs (know better as processes) that run in the background such as time and date updating, messenger services and networking. Some of the processes are open to attack and misuse by virus writers. They target ports that are not protected.

A firewall will block unused or unnecessary ports, it gives you chance to decide which programs and process can have access.

2. Antivirus

A computer virus is a program that has really bad intentions. Once your computer has been infected it can be used to carry out tasks designed by the virus writer. Tasks such as attacking other computers to stop them working (denial of service), send out spam email and to steal any information deemed worth while.

An antivirus program attempts to detect existing viruses and try to work out new ones based on what it already knows. Wikipedia defines the two methods in which viruses are detected...

Signature based detection is the most common method. To identify viruses and other malware, antivirus software compares the contents of a file to a dictionary of virus signatures. Because viruses can embed themselves in existing files, the entire file is searched, not just as a whole, but also in pieces.

Malicious activity detection is another way to identify malware. In this approach, antivirus software monitors the system for suspicious program behavior. If suspicious behavior is detected, the suspect program may be further investigated, using signature based detection or another method listed in this section.

There is more but I will leave you to read the rest on Wikipedia.

3. SpyWare

The third level of protection is to stop bad software from spying on your actions. From watching which websites you visit and stealing your passwords and credit card details to logging your keyboard activity.

Many spyware programs arrive via your web browser so it is important you use a program and browser that can warn and protect you against infection.

These programs install themselves, like viruses, with out your knowledge or hide inside other programs.

4. Keeping your system upto date.

I am sure that when your computer prompts you to install an update you allow it to happen. These updates often install changes that offer greater protection and get rid of bugs and flaws that allow malicious software to take advantage.

Most modern operating systems such as Windows, Mac OS X and Linux, will tell you when an update is available. Normally a single click will get the update installed.

5. You!

You can protect yourself by being carefull with the emails you open and the programs you install. If you are unsure then use a search engine to see what other people are saying about the program or product you would like to use. A good guide would be, if in doubt – don't.

There are many paid-for solution to protect your PC, such Norton etc. However there are many free programs that you can download and give excellent protection.

ZoneLabs Zone Alarm (firewall)

AVG antivirus

SpyBot search and destroy (anti spyware)

Don't forget to perform regular updates to make sure your protection is current and aware of all the latest problems.