The true answer, based on my experience, is sometimes! I love AVG, it's a great program! It finds most of the known viruses, which still flood the internet. However, what I've found is that some of the brand new ones, or ones within a year or two old, are still able to bypass its security! Viruses like the "xp defender," a fake anti virus program, actually in some cases prohibits you from running AVG! Overall, I think it is a great program. It certainly works to keep you as protected as it can, based on what it knows, as well as your continued updates to ensure the program has current virus definitions.