A computer virus is a malicious program or set of files which degrades and affects the performance of a computer. At times, it also results in improper functioning of a computer or operating system. A virus can spread from one computer to another when they are connected through a network. Removable media such as pen drives, memory cards, floppy disks etc. have been traditionally some of major sources through which viruses used to spread in the past. However, Internet has now replaced them as the key source of most malicious computer viruses. Most of the viruses are man-made programs created by unscrupulous people with malicious intentions. Some computer viruses have also been seen to steal important financial information from your computer in conjunction with spywares and so, you would always like to protect your computer from viruses. For this purpose a set of software known as an 'anti-virus' is available. An anti-virus software is a set of program or files that scans your computer memory and tries to delete or deactivate any virus present in the system.
There are many anti-virus software available in the market and on the Internet. Some are free to install while you need to pay for others. However, none of them are foolproof and a single anti-virus can not detect each and every computer virus. A computer which is connected to the Internet may need a highly rated paid security solution whereas a computer which is not connected to the Internet may require a basic freely available anti-virus. It also depends on the websites which you normally visit and your browsing behavior.
If you visit only a few trusted sites and do open strange emails then you might not need an advanced one. For proper research on which solution would suit you best, you can visit different tech forums on the Internet to gain knowledge about different anti-virus software. You can also check third-party lab tests for various anti-viruses to get an idea of their reliability. Moreover, reviews at popular software download websites such as softpedia, cnet, brothersoft or softonic can help you in deciding on the right one for your needs. For an average home user using a Windows Operating System, the security suite Microsoft Security Essentials which is freely available from the official Microsoft website may work out very well for all your security needs. Once you decide on the desired anti-virus, you can download it and install it if it is a freeware. If it is a paid one then you can purchase the license for the software and install it.
But once an anti-virus software is installed, most computer users forget to update the virus definitions in their software. When they face a computer virus related problem in the future they complain about the software developers and the vendor. But that is where they make a grave mistake. A person who is connected to the Internet must understand the fact that new computer viruses are discovered every single day and so, it is of prime importance to update the virus definitions regularly. If you are connected to the Internet all the time and do not care much about safe browsing then there is a likelihood that your operating system might be a prime target of such malicious viruses.
So, you need to make sure that your Operating System and security software is well equipped to handle such viruses including the latest ones. To do that, you need to update the virus definitions in your anti-virus software everyday. Most paid anti-viruses would automatically update the virus definitions everyday but in case of some free ones, you might need to update them manually. The updates are free of cost for the lifetime of a free anti-virus whereas it is free for the licensed duration in case of a paid one. You must make sure to check the virus definition details every few days to make sure it is up to date. Most anti-virus software would show the last updated date and version number of the virus database within the software itself. However, even a regularly updated anti-virus can not guarantee 100% safety from virus and malware and so, I would advise you to install an anti-malware / spyware with it to be safe from any virus and malware related threats.