Google will label sites in their search results as harmful, when the site is believed to have malware on it. The last thing Google wants to do, is help an unsuspecting searcher land on a web page that can infect your computer. So Google takes a proactive approach to discovery and labeling malware results.
But sometimes, your site can be found to have malware. Malware can get on your site through being hacked or through third party code. If you find this label on your site, you need to remove the malware from your site and notify Google that it has been removed.
After it is removed, go to Google Webmaster Tools and there will be a place to request a review. Go through that process and then hopefully, within a few hours, that label will be removed.
Google has a detailed post on this at the Webmaster Central Blog. That post and in a recent thread at Google Webmaster Help, it says, it typically takes hours to remove the label, but can take as much as a day.
Webmasters are eager to have a Google malware label removed from their site and often ask how long a review of the site will take. Both the original scanning and the review process are fully automated. The systems analyze large portions of the internet, which is big place, so the review may not happen immediately. Ideally, the label will be removed within a few hours. At its longest, the process should take a day or so.
Forum discussion at Google Webmaster Help.

Comments:
fromNamibia
01/31/2009 03:22 pm
All sorted now, checked with both IE and Firefox. Thanks tech support at Google. If only all issuses in IT could be resolved so fast.
Pat
01/31/2009 03:23 pm
Alien attack thwarted! Well, at least for now......
kathy
01/31/2009 03:23 pm
I just had this happen, too! EVery result in Google said the thing about "may be infected." So I restarted my computer - and then things appeared to be back to normal.
MahmoodSultan
01/31/2009 03:23 pm
google had solved problem................... now working welllll
hydra
01/31/2009 03:24 pm
thing went normal now
Steve
01/31/2009 03:25 pm
Problem appears on Safari as well.
Jack Christopher
01/31/2009 03:26 pm
Happening to me too. I'm not sure if it's fixed yet.
mary alice
01/31/2009 03:26 pm
going to yahoo search as I type...this is too screwed for words
Steve
01/31/2009 03:26 pm
awww, some people don't like Bush because their Daddy wasn't nice to them when they were kids.
Lynn
01/31/2009 03:27 pm
Interesting - we have a web site that was resulting in "This site may be harmful..." - however, if you got to our sites through one of Google's sponsored links (which our company pays Google for each click) - then our site was okay - not harmful. So, if you pay for the link - you're good.
Lynn
01/31/2009 03:29 pm
It looks like Google fixed whatever was going on - it works for me now.
Ian Ryan
01/31/2009 03:30 pm
I have the same probem. It seem that Google itself is sending malware to your PC or MAC. If you empty your browsers cache, The problem goes away!!!!!. Check for malware and hope Google identifies and solves the problem soon... CLEAR THE CACHE!!..
pissed off
01/31/2009 03:32 pm
can someone post a decent search engine that ACTUALLY WORKS and doesnt block every page i click on? I am going to uninstall EVERYTHING Google if this isnt fixed SOON
Maruthi
01/31/2009 03:33 pm
Google is updating all the links under its server.. this would be sorted out in next couple of hours.. guys don't worry.. its our google
Nefariousster
01/31/2009 03:35 pm
Guess Google will sort this out in a day. But google will loose a lotta its fans for sure even thought we have a work around
Carrie
01/31/2009 03:39 pm
fixed.
Sue
01/31/2009 03:40 pm
Today I have the same problem. All my google search results will harm my computer according to Google. This is a worldwide problem of Google. Is Google Search Engine under yearly maintenance?
lynda
01/31/2009 03:43 pm
no matter which website i have tried to go to, everything states that this may be harmful to your computer. i even received that from yahoo. what's happening???
jfzk
01/31/2009 04:01 pm
seems to have beenm fixed, or is that just me?
deanz
01/31/2009 04:11 pm
loooks like its have been fixed. really stunned me.
yes
01/31/2009 04:13 pm
Job openings at google!!! I think that it is time for us to apply for a job at google (because almost certainly someone will get fired...) Big oportunity!!! http://home.deds.nl/~antispam/
Rob Abdul
01/31/2009 09:07 pm
My theory is that it is nothing to do with Google, you’ve got spyware that was dormant till now.
Vickie
02/21/2009 05:17 pm
We have this coming up for our site and it was hacked, got our website host to clean it up after I had checked all the files and reloaded, but it was still there. It is clean now but the site is still labeled, to try to get the label removed I have to open an account with google and put some code of theirs on our site. This is ridiculous, it is great that they found it, but sucks that you have to add code from them after opening an account to get them to check your site again, which is not a given as to when they will do it. Have lost traffic because of this.
JOCK
06/13/2009 05:48 am
Baby look yall need to fix google...its messing my computer completely off...PLEASE FIX GOOGLE OR KEEP IT OFF MY COMPUTER!!!!!!!
morrison
04/05/2010 02:58 pm
every time i look at my bank statement i am blocked by webmaster proactive scanner.could i have this removed so i could do simple on line banking?