Avast Melts Down

**Viktor_Olin** · 12-05-09, 09:56 AM

Any Avast users have the false positives issue this week? A definition update flagged multiple legitimate files as threats and moved or deleted them, crippling hundreds (if not thousands) of users' PC's in the process:

http://blogs.pcmag.com/securitywatch...bels_files.php

http://news.cnet.com/8301-1009_3-10408645-83.html

http://blog.avast.com/2009/12/04/apo...nition-update/

Very disappointing performance from my favorite free AV. Luckily, I dodged this mess, but it's made me switch to Avira AntiVir Free, at least for the time being.

I had just installed Avast 5 Beta3, which has a great GUI and looks like a really promising upgrade, but it flagged two legitimate files as malware and moved them to the Virus Chest (quarantine), even after the corrected definition update. And it did so with no notification that I could see. It appears Avast 5 also does not give you the ability (that I can find) to ignore potential malware, so any file it flags as malicious is going to be moved automatically, requiring you to restore it.

Teaching points: don't blindly trust your antivirus software. Check the settings and be sure you retain some measure of control over file deletions in the event of a false positive. More importantly, backup, backup, backup! Find and regularly use a good backup or imaging program (I like Macrium Reflect Free). Imaging software has saved my butt many, many times over the years.

**RuddlesPub** · 12-05-09, 11:48 AM

it happend to me and I deleted a .dll, now when i start my computer up i get a error that some program cant start. dont know what to do

**WileECyte** · 12-05-09, 11:58 AM

I gave Avast a try when I went to Windows 7. It seemed a lot more bloated than Avira, which I ran under Vista. I ended up going with Microsoft Security Essentials since AV Comparatives gave it a good review.

**Viktor_Olin** · 12-05-09, 01:42 PM

Originally Posted by RuddlesPub

it happend to me and I deleted a .dll, now when i start my computer up i get a error that some program cant start. dont know what to do

If you have completely deleted the file, you may have to re-install the program. You could search for the .dll file on the web, but even if you could locate a copy, you'd have to know exactly where to place it. It isn't in your Recycle Bin, is it?

You might try a file recovery program such as Recuva (http://www.piriform.com/recuva). I've never had to use one of these, myself, but it might be worth a try.

**HeavyG** · 12-05-09, 07:20 PM

That sucks... I really liked Avast. Oh well, I won't install that again.

**Phyrelight** · 12-05-09, 07:47 PM

I didn't have my PC on during that time so I didn't receive the update, no problem encountered here /whew

:10 :10 :10 :10

**Langrad** · 12-05-09, 10:13 PM

Somewhere in windows is a small thing that lists what files your computer tries to open on startup. Many Trojans install .dll's and makes the computer think they are legitmate and once removed you get the error box. Found out a few weeks ago (after 2 years of bootup error boxes) that useing this startup thing you can uncheck the .dlls and the boxes wont pop up anymore.

**Too Much Damage** · 12-06-09, 01:08 AM

That really sucks. avast is my favorite free av. is there any news as to why exactly those files were flaged?

**Viktor_Olin** · 12-06-09, 07:54 AM

Originally Posted by Too Much Damage

That really sucks. avast is my favorite free av. is there any news as to why exactly those files were flaged?

http://blog.avast.com/2009/12/04/apo...nition-update/

Just a totally fubar'ed update file, apparently.

I might give Avast 5 another look in 6 months or so, after they've had time to get the bugs out. I suspect that after this mess, they'll be even more diligent in assuring that nothing similar happens again.