Protecting over 200 million PCs, Macs, & Mobiles – more than any other antivirus

April 12th, 2011

Follow-up instructions for “False positive issue with virus defs 110411-1″

On 11 April 2011, virus definition update 110411-1 contained an error that resulted in a high number of ‘false positives’ – that is, clean websites or files being flagged as ‘infected’.

Our virus lab staff discovered the problem quickly, took precautions to stop more users from getting the wrong update and, about 45 minutes after the initial update, released a fix (update 110411-2).

About 4% of our user base was affected.

Although false positives are a fact of life, we sincerely apologize for any inconvenience caused to our community. If you were one who was affected by the bad update, after updating with a current virus definition file (as of this writing, update 110412-0), you should next:

  1. Open the avast! program
  2. Select “Maintenance”
  3. Select “Virus Chest”
  4. Sort by time moved to Chest
  5. Select files you wish to restore
  6. Right-click and select “Restore”

After the file restoral, copies of the files will remain in the Virus Chest.

We hope these steps will alleviate any confusion, but should anyone need further support, please visit

  • Jayme Rehder Neto

    Não consigo baixar o meu AVAST , já esta pago e eu estou com o LT sem defesa. Grato
    Jayme Rehder

  • 12-es_csaj

    I was using my computer all evening and for a long time at night. But I wasn’t affected.

    My avast! is being set to try to update in every two hours, but it couldn’t update to the bad 110411-1. I am fortunate; but it’s not only fortune. You prevented some users from being affected by shutting down the update servers.
    My avast! tried to update at 10.10 pm, but it didn’t succeed.

    Thank you the fast measures!

  • Lord Stephen Belez

    I’m not affected with this, but thanks for the warning and for the precautions!

  • Christine G.

    I was affected and unfortunatly deleted files from the virus chest before getting these instructions. Hope it hasn’t messed up too much. It did come up with a ‘Trojan Horse’ warning on a new website, I hadn’t been to before, and then on several other ‘safe’ sites. Thanks for letting us know about this though.

  • Bill D.

    I am using avast pro that I purchased, I wasn’t affected by this at all but I did notice my avast would not update until it was fixed with a new update. I think most of the problem was with people that changed it to delete the files instad of putting them in the virus chest. I also noticed some people panicked and deleted them right away, also do research before deleting anything found it does no harm to leave it in the chest.

  • Jason

    Maybe the Avast default should be to move the files to the virus chest. Removing the delete option completely would be a really good idea.

  • Ronald Sweeney

    Yes I was affected! Thankfully it was almost end of my shift. Later in day everything worked ok. Thought I had a virus that said I had a virus as I could not go to any of my work sites.

  • Malinda bandara

    Thanks for the warning. avast!

  • Michael

    No Problems here.

  • paraxeno

    latest definitions shown in my version are 110413-0 – is that correct? cause in your post you mention previous one

    thanks :D

  • nicholas

    i was infected and had to re-install windows, but avast is still my number1 anti virus :D

  • http://windowslive Murray

    I got tired of all this crap…So I uninstalled it and out it went with all that was in the virus chest….Then I installed it with-out the virus updates….then I registered it…and now no problems….took me just 10 minutes to fix my problem.

  • choirul nasihin

    it doesn’t matter,,,
    i none affected by it.
    thanks avast !

  • abdul ahad

    nice work

  • Pat

    not effected by false positive

  • President Obama

    Nice job Avast!!!

  • herman

    I was not connected to internet on 12, then I think that definition was not updated

  • jose jaimes

    Avaast es un antivirus buenísimo , soy de Venezuela quisiera que por favor la cuenta se cancelara en bolívares , ya que quiero adquirir el paquete y la calidad que tiene Avast . Verdad gracias por su servicios , agradecido si toman en cuenta mi petición, sin mas que decir me despido de ustedes . Continúen realizando un buen trabajo, quien les agradece.

  • John E

    All Well and Good that the fix was sent out 45 mins later, Avast blocked all Websites from sending anything to my PC and over 900 files showed infected and the recommended boot scan showed so many files infected that they had to be deleted since there was no room on the so called allotted disk space. Ultimately I had to do a “new out of the box” restore from the D partition since the P/C was not running correctly. Thanks alot for the 2 days of downloading updates and installing programs that did not come with the laptop. Like I had nothing else to do

  • Archangel

    I do not know how, but I was unaffected by this. I use Avast 6.0 and I did not have this issue. I had 2 sites that were supposedly infected, and they were on ad.harrenmedia, but that is about it. And it is possible that those infections may have truly been real. They were iframe infections. Lucky me!

  • Otto.C

    It is April 20, and the problem is back. I can’t access, which is most definitely not infected!

  • bigcitylib

    April 20th, and I cannot get to Hotmail or elsewhere. Also server overloaded to download any new update.

  • Otto.C

    I have just manually updated the Virus definitions, and the problem has vanished.

  • Jason Mashak

    bigcitylib :

    April 20th, and I cannot get to Hotmail or elsewhere. Also server overloaded to download any new update.

    I just checked with the Virus Lab and everything seems to be fine on our end. Try again?

  • bigcitylib

    @Jason Mashak
    Was able to download successfully about half hour after I posted. Everything is OK now.