I'm using Avast antivirus and it has this "scan your computer" option. What would be the purpose of using this function, as one would think that the program should block eventual hazards before they get into the system? It would be like to buy a bag full of groceries (without checking the dates) and then when you get home you notice that some of the products are out dated, and you have to throw them away.

new virus definitions are added everyday, you may want to perform a scan after an update for example.

Some viruses might be sitting on your computer waiting to be executed (by you clicking on them, or some other program executing it).

It's better to scan to make sure there's nothing to worry about, just in case the virus detector doesn't pick up the virus when it's executed.

Don't ask me Why it wouldn't get picked up, but I imagine it's possible.

new virus definitions are added everyday, you may want to perform a scan after an update for example.

Thanks. I have to admit that I didn't thought of that. I'll get my coat.

Yes you need to give your computer a full scan at

least once a week, as Avast should be updating

its self with new definitions,at least once everyday,

I also scan with Hitman Pro and Malwarebytes both

free and they catch what your main Antivirus misses,

regards Worgeordie

new virus definitions are added everyday, you may want to perform a scan after an update for example.

Thanks. I have to admit that I didn't thought of that. I'll get my coat.

Hackers are finding many devious ways to get viruses and malware onto computers, in email attachments, on removable media, in zip files etc, etc. I think it's a good idea to do a regular scan of your computer even if it's just for peace of mind.

as a good practice, boot from a CD or an USB, then perform a full scan. a regular daily scan, then just perform it from the application, don't need a boot scan.

boot scan identifies hidden virus inside the system layer too.

Don't ask me Why it wouldn't get picked up, but I imagine it's possible.

It is very possible that you may get a new virus before the virus programs are aware of existance and the virus database updated. This means the virus will get through your normal defences and remain undetected until you do a scan with a newer virus definitions file installed.

Some viruses also have the ability to disable virus scanners, and until that is fixed in a later release these viruses will also remain undetected.

It's not like you need to get out in the sun and shovel anything, and it doesn't cost anything. I have mine set for a daily full scan.

If it goes off and effects performance when I am busy (work,games, porn etc) I just cancel the scan and it will pick up again the next day.

Another school of thought on this, is that as long as your Anti-virus software has Real time detection built in and enabled, full system scans are both a waste of time/ resources and can actually do more harm than good.

This was the argument made by one of my former colleagues, Dr. Peter Tippett. Peter is credited with being the father of the anti-virus industry as he was the original developer of the Anti Virus program that eventually became Norton AntiVirus. He was also the head of research at ICSA Labs. The logic behind is argument is that:

1.) Real time anti-virus detection would detect any virus when that file was accessed. File access occurs constantly, whether it be the user clicking on it, the operating indexing it for search functionality, disk defragmentation, backups, etc, etc, etc. This means that scheduled scans are completely redundant and unnecessary.

​2.) In a corporate environment, anti-virus system scans can be resource intensive and intrusive to the end user. In addition to the costs of lost worker productivity, the endusers will often times attempt to circumvent these protective measures by disabling AV programs all together and thereby actually increasing the risk of infection exponentially. Additionally, given that most corporate work places utilize primarily mobile laptops that are usually taken out of the work place on nights and weekends, scheduling scans for "off hours" is not realistic. What generally happens is that the scan will kick off when the machine is powered back on in the morning, right as the user attempts to start their business day.

Having done corporate network security for many, many years, I have seen this done both ways (with and with-out full system scans). Its been my experience that the work places that do NOT have scheduled system scans actually see a slightly less or equal rate of incidence. End users are generally happier and more productive, not dealing with scheduled scans and face no additional risk. All the evidence I've seen in my 15+ years in the computer security industry definitely supports the argument made my Dr. Tippett.

-Mestizo

On the same subject, another thing Peter like to say, was that doing daily AV signature updates was only 1-2% better than just doing weekly updates.

The logic here is that any decent AV application should have good heuristic detection built in. Playing a never ending game of whack-a-mole doing exact pattern matching of every virus created, is not really sustainable.

-Mestizo