Microsoft Security Essentials wrongly detected Google Chrome as being a password stealer and a variant of the infamous Zeus trojan. This mistake affected nearly 3000 Chrome users as they couldn’t access or even find their browsers on Friday. The .exe file was removed by the AV.
Microsoft quickly made the necessary changes to its definitions by released an updated signature (1.113.672.0), though MSE users can also manually update their protection and reinstall Chrome.
On September 30th, 2011, an incorrect detection for PWS:Win32/Zbot was identified and as a result, Google Chrome was inadvertently blocked and in some cases removed from customers PCs. We have already fixed the issue — we released an updated signature (1.113.672.0) at 9:57 am PDT — but approximately 3,000 customers were impacted. Affected customers should manually update Microsoft Security Essentials (MSE) with the latest signatures. To do this, simply launch MSE, go to the update tab and click the Update button, and then reinstall Google Chrome. We apologize for the inconvenience this may have caused our customers.
To manually update the AV, read the instructions HERE.