Anti virus is most important need for PC protection and against internet. Kaspersky, Aveera, Quicl Hela, AVG, Norton, Avast, Microsoft and lot others are different anti virus for PC. But I suggest AVG anti virus, as it is very nice, speedy and completely keeps our computer virus free. When ever any external drives or pen drives are attached to the PC, AVG first scan completely an if no virus is found then only access is allowed. On internet when you are opening any page, it first signal you that the page is virus affected and will not open that page.