First and foremost, since viruses, Trojans and other malware are a major concern for any computer connected to the internet; By a survey it is recorded that mostly virus hit your system with the increasing use of USB flash Memory, and new forms of viruses are always getting updated with passage of time, Even Viruses have changed their forms.
Now you can find a virus in a jpg image also, which look so odd, They can attack your computer with a unknown news resource, or they can jam your system if you accidentally reach to a site which you don’t know, So safe browsing is the key to avoid such issues, one should be sufficiently prepared to defend one’s PC from such things by a good antivirus program.
There are plenty of proprietary antivirus vendors such as Symantec and McAfee that have been in the antivirus business for years. However, since purchasing their products cost a pretty penny and unless you continue to pay subscriptions to update your virus definitions the program essentially becomes crippled, this is not necessarily the best solution. There are several free antivirus programs available on the Web that are not only easy to use and update but also offer equally powerful protection.
AntiVir, avast! and AVG are three programs that offer robust immunity against the most vicious viruses roaming the internet. Of course, there is always the option of not using antivirus software and finding all your data wiped out or worse. Your computer hijacked and turned into a zombie slave. The zombie does what ever is kept in its memory.