What does anti-virus software do?
Anti-virus software scans files or your computer’s memory for certain patterns that may indicate the presence of malicious software (i.e., malware). Anti-virus software (sometimes more broadly referred to as anti-malware software) looks for patterns based on the signatures or definitions of known malware. Makers of Anti-Virus find new malwares on daily basis and update their Anti-Virus accordingly, so it is important that you have the latest updates of Anti-Virus installed on your computer.

Once you have installed an anti-virus package, you should scan your entire computer periodically

• Manual scans – If your anti-virus software does not automatically scan new files, you should manually scan files and media you receive from an outside source before opening them. This process includes:
• Saving and scanning email attachments or web downloads rather than opening them directly from the source.
• Scanning media, including USB Flash Drive, External Hard Disk, CDs and DVDs, for malware before opening files.
• Automatic scans – Most anti-virus software can be configured to automatically scan specific files or directories in real time and prompt you at set intervals to perform complete scans.

How will the software respond when it finds malware?
Sometimes the software will produce a dialog box alerting you that it has found malware and ask whether you want it to “clean” the file (to remove the malware). In other cases, the software may attempt to remove the malware without asking you first. When you select an anti-virus package, familiarize yourself with its features so you know what to expect.

Which software should you use?
There are many vendors who produce anti-virus software, and deciding which one to choose can be confusing. Anti-virus software typically performs the same types of functions, so your decision may be driven by recommendations, particular features, availability, or price. Regardless of which package you choose, installing any anti-virus software will increase your level of protection.

It is a good idea that you install anti-virus software if you don't have any already. You can download Microsoft Security Essentials (free for personal use)

It is essential that you download updates of anti-virus software regularly over the internet. Out-of-date anti-virus software will have flaws and may not work properly.