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Currently, I'm using Avast. But I hate that it makes my computer start more slowly, and in the 90% of the cases I don't even use it, it's just a deadweight. No it's like this with every other AV product. (Avast is great btw.)

Is there a resident protection so I just launch it and it'll protect my PC onward?
Or is it possible to make Avast / MSE on-demand somehow?

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up vote 4 down vote accepted


Avast! includes, by default, an always-on, resident scanning service. You should never turn this off, as doing so will leave your system much more vulnerable to infection.

Indeed, an on-demand-only scanner may detect and clean malware for you. But, without a resident component active, it can only do so after you've been infected and damage has likely already been done.

If you really feel that you must disable resident protection, Avast! does provide that option. Still, I strongly recommend against it.

It looks to me like a few things may need to be clarified, here.

"Is there a resident protection so I just launch it and it'll protect my PC onward?"

Yes, and Avast! is one of them.

Most antivirus products for Windows - Avast! included - have three basic components:

  1. On-demand scanning application.
  2. Resident protection service(s).
  3. Updater service.

Items 2 and 3 should be (and, by default, are) always running. These are the services that ensure your system is protected around the clock.

"in the 90% of the cases I don't even use it"

This is entirely untrue. Whether you realize it or not, you are using your antivirus software 100% of the time that you are using your computer. This is because of the #2 component listed above. Every time you run an application, open a file, or even browse a web page, Avast! is checking to make sure that everything is clean.

"Or is it possible to make Avast / MSE on-demand somehow?"

It may be, but most antivirus products protect their resident services from being disabled. In the end, I'd recommend against it anyway.

The resident service is a proactive defense - the best kind. It is constantly checking the code you're running on your computer before it actually gets executed, preventing malicious software from ever downloading or operating at all. Take away this functionality, and you're only left with reactive defense - one that operates after the malware has already found a home on your computer. If you rely only on scheduled scans, there's a fair likelihood that you will find yourself with an infection that will not only be impossible to remove (requiring a re-build of the system) by the time you detect it, but will also probably go un-detected for awhile because it has had plenty of time to hijack your antivirus when you weren't watching.

Regardless of which antivirus product you choose, the resident services really are the most essential parts. While regular on-demand scans are still recommended, full-time resident protection practically renders them obsolete. The down-side of this is that there is some additional overhead added to the boot-up process, as well as any file system operations, but the security enhancement gained is well worth it.

That being said, there is an option to disable the "shields" (as they're called in the program) in Avast! Right-click the Avast! tray icon, and hover over "avast! shields control". You will have options to disable for 10 minutes, 1 hour, until next restart, or permanently. Again, I recommend strongly against using any of these.

If performance is an issue for you with Avast! there are other free antivirus scanners that perform similar functions. Microsoft Security Essentials, AVG, and Avira are among the ones I see most recommended, other than Avast!. Perhaps those will fare better on your system. In any case, I cannot emphasize enough how important it is to keep the scanner's services running in the background always.

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Microsoft have made a big point of making sure MSE is less resource hungry than the competition (being AVG, Avast etc) and in my experience it is way better behaved on start up as well. – Rory Alsop May 4 '11 at 15:01
@Rory - Though, it's got a really slow scan speed. – Shiki May 13 '11 at 11:03

ClamWin is an on demand only scanner you can use which can be used just to scan on demand.

Alternatively, you can use pretty much any AV product on the market and just disable its on demand/active component.

I can not speak specifically for Avast, but some are much better than others and you may want to try changing AVs to see if there is a faster one for you.

Also, a subjective method to speed up AV which I cannot really recommend is to exclude folders such as program files, your profile, the windows folder etc. and just make sure you include your download location, temporary files, internet cache etc.

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The problem is the start up mostly. It takes a lot of time to load, and you can't really delay it. I'd like to make it load on-demand. Then, it can stay as long as I want. LIKE when you go into battle, you put on your kevlar vest. When it's over, you take down your stuff. That's what I want in short. ^^" – Shiki May 3 '11 at 23:10

It's been too long since I last used Avast, so I can't speak for it anymore, but many (most?) AV products function by installing themselves as a service set to start up automatically. You could change this to make them start manually, and then you should get your fast boot-up back while also being able to quickly and easily turn on the resident scanner (by starting the service).

Not all AV products work this way, though, so are simply memory-resident programs launched during start-up. You could try tracking down and disabling whatever mechanism launches them (probably a Run key in your registry somewhere), but you'll likely find that they'll simply re-enable that the next time you do start them up.

Alternatively, you could find a different AV product. I've been very happy with Microsoft Security Essentials (formerly an alternate Avast/AVG guy), and it's pretty much the lightest AV I've ever used, with no noticeable (to me, anyway) difference in start-up time or system performance after installing it.

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