Whether you have recently purchased a new computer or just want to secure your old reliable (or not so reliable in some cases), there are so many different types of antivirus software out there that it is almost impossible not to find something that will please you.

Although not tangible, antivirus software comes in different shapes and sizes, literally. The layout of the software can vary depending on which brand and which distribution you purchase. Subsequently there are two decisions you need to make when you buy antivirus. Three if you include your budget range within the decision process.

The first thing to consider is 'do you need antivirus software'. Some computers do not require protection, such as apple macs and linux based operating systems. Secondly, you should consider what brand you should purchase. Usually one would think that comparing antivirus software is like comparing eggs with eggs; they are the same. But this isn't always the case. Many users have different opinions on antivirus software.

Ultimately the decision is yours. People tend to choose the application with the biggest market share, such as McAfee or Symantec. However, this is not such a good idea with so many better but lesser known products available.

You might want to visit sites that offer reviews on antivirus products. Some retailers allow the purchaser to return and write a review on the product they purchased. If you use this method you will most likely get a range of honest reviews from both novice and power users.

The next and best method is to is to simply trial a selection of products prior to purchase.Most antivirus products are available for a 30 day trial prior to purchase. This enables you to take a test trial and ensure the product is suitable for you and your computer before you part with your hard earned money.

Ultimately, because software can be easily uninstalled and replaced, you are rarely forced to stick with any provider for any means. Antivirus internet security software is not an exception. So go on, trial some software and purchase the one that's right for you. If after a while you change your mind, you will only have to wait for the remainder of the licence before you are able to swap for a different brand.

Antivirus software is a pc program that detects, identifies, prevents and takes action to disarm or remove malicious software programs such as viruses and worms. Malware (which is derived from combining the terms malicious and software) is the term generally used to refer to such harmful programs.

Let us look at some of them:

Viruses: These are programs that attach themselves to other programs or documents and replicate to cause damage to PC.

Worms: These are specifically designed to make extensive use of emails to spread rapidly.

Trojans: These are typically programs which appear harmless but are damaging and malicious in intent.

Zombies: Are programs that install themselves on PCs and remain dormant until an external event triggers them into action. They can damage the computer, steal personal information to transmit it to an unauthorised email account or even set up a remote control access to one's computer.

All of these malware are referred to as viruses in common parlance.

Antivirus is intended to prevent, detect, disable or remove from the PC all malware which is done by the antivirus engine which scans the PC to look for tell-tale signs of these malicious programs. This is called signature based detection and involves searching for known malicious patterns in executable code.

Once detected the software takes action such as to clean, delete or quarantine. However, it is possible for a user to be infected with a new virus with no signature existing. These viruses can be detected by looking for known malicious code or slight variations of such codes in files.

It is important to understand how viruses spread. With increasing use of the internet the most common route for their spread is obviously through email. They can also spread by sharing disks, network drives and by internet downloads. They can not spread on their own and must be run or executed by some one to cause damage.

Viruses can infect the boot sector ot the PC if the user inadevrtantly, boots his PC from an infected disk. Other viruses can spread by simply opening an infected document.

In order to efficiently counter such threats, one needs to buy antivirus software that is updated regularly, is easy to use, detects and cleans all threats, and offers a comprehensive computer protection package such as Kaspersky Antivirus and Kaspersky Internet Security.