Will an Anti Virus slow down my computer

My computer came with a free version of Norton and I have been using it ever since. But I keep reading that antivirus software will slow down my computer and that norton is one of the worst at doing this.

Is there any truth in that, and can I stop it from happening?

Wherever I've seen this question asked, the response is always the same. The anti-Norton brigade leap to the attack and defend all the freebies like AVG. The Norton users usually stay quiet because they can't win against however good Norton is. It then usually descends into polarised views with everyone stubbornly standing their corner. All will say they have never caught a virus with 'their' virus checker!
All will slow down your computer by some degree. Such is the nature of 'live' protection.
Question you have to answer is, "What are the risks?". If you don't use email and never visit 'dodgy' sites then you will have a lot less to fear than those who do!

I run one machine purely for video editing. It has no virus checker and only the Windows Firewall. The only online activity is updates! It has never (knowingly) had a virus!

Yes they can slow your PC down (some more than others). It really depends on your AV settings and how it is configured to scan.

Scanning "on access" means that you will have great protection as it will scan each application every time you run it. "On demand" will only scan when you manually check an application, so although your PC will faster - it's next to useless, as the one time you need it, it won't be running. Usually there's a compromise in a "smart scan" that only scans a file if it hasn't been checked before, or if it has been modified since.

Like Ian and Geo said, they all will especially the big competitors like Norton and McAfee. This may be wrong, but it's my experience. AVG and Live OneCare are rather speedy, but no matter what you do, you're still going to notice even a slight change.


NOTE: I was about to say "Good luck and Cheers!" but I just decided to put it into my sig.

I wouldn't like to risk my computer without any antivirus software so I will keep things as they are for the moment. It should be much faster so I won't notice it as much

I was wondering if it would be possible for someone to make something like a "Security Processing Unit (SPU)," or some other name, similar to what a GPU (Graphics Processing Unit) does in moving a lot of the graphics processing (or in this case security processing) away from the main processor. It could even have its own RAM memory much like a GPU video card does. An "SPU" card could be placed in a standard PCI slot and you could choose any security software you want that can work with the chipset. It could also maybe have SATA pass-through connectors on the card where all hard drive activity could be scanned in real time on the "SPU" without slowing down the main processor or hard drive access times by just listening in to the data being transfered and notifing the operating system if something is detected. It always seemed a bit much to scan every file on the hard drive everyday with a scheduled scan. The files can't do any harm until they are loaded off the hard drive into memory anyway, so it would make more sense to just scan files when they are read or written and the "SPU" wouldn't slow your computer down any.

Such a thing (kind of) exists already At the moment they are just mini-PCs that act as a gateway to your information, essentially running AV software on dedicated hardware where possibly to scan internet/e-mail traffic. I don't think that there are SATA pass-through ones though (as far as I know).

Would be great if they did exist

Would it be possible to designate a core or two for security - Almost in the way that error checking works in memory

Create it, patent it, and sell it. You would make millions.

That would be an idea and a half. "GWest SPU". Do it.