Norton have even been caught releasing virus as have other large av companys, the multitude of free anti-virus online are equally good and in many many cases a vast improvement upon their paid for alternative.

Having tried a few free AV, the three that top my own & most others lists are,

in order.

Avira
Avast
AVG

I currently use avira and have done for sometime.

I have tested a lot of AV programs like:
Norton (of of the poorest programs I have ever inflicted upon my poor computer).
Zonealarm which is ok but will slow down your system and doesn't catchall.
Mcaffee is mediocre at best.
Kapersky, seems effective but produces a lot of false positives.

The free ones I tried seemed effec...

Norton have even been caught releasing virus as have other large av companys, the multitude of free anti-virus online are equally good and in many many cases a vast improvement upon their paid for alternative.

Having tried a few free AV, the three that top my own & most others lists are,

in order.

Avira
Avast
AVG

I currently use avira and have done for sometime.

I have tested a lot of AV programs like:
Norton (of of the poorest programs I have ever inflicted upon my poor computer).
Zonealarm which is ok but will slow down your system and doesn't catchall.
Mcaffee is mediocre at best.
Kapersky, seems effective but produces a lot of false positives.

The free ones I tried seemed effective enough until I tried Avira which is what I use currently.

The reason I use it is this; I tested the various AV programs out over a 2 month period with Avira being the last one I tried being Avira. I ran scans with each, looked at the auto-protection of each and other things. but what made me stick with Avira was that when I ran scans with it, it picked up and killed 12 Trojans!!!!!

I was like, what the hell? and with good cause how is it possible that many could be on my computer after so many recent full scans by so called industry leaders?
The reason is this, viruses are not born, they are created by hackers (and other government agents. lol) usually for a specific purpose, that is right, most are in fact malicious programs (hence malware).
A high proportion of viruses are coded to be able to deal with the most widely used Anti-Virus and firewalls. quite often your bought and paid for AV program wont even pick up certain viruses.

Although it should be said that just because you have one on your computer doesn't automatically mean there is someone on the end of it waiting to get in to your HDD.