Microsoft said the case of mistaken coding identity lasted about three hours and affected about 3,000 users.

"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" (personal computers), Microsoft said at a malware protection Facebook page.

An update to free Microsoft Security Essentials anti-virus software had mistakenly targeted Chrome as a troublesome computer virus tailored to steal online banking information. Microsoft apologized for the error.