Bangalore: Microsoft had issued a warning about a potential bug in Internet explorer browser, which hackers are already exploiting to take control of the remote systems. The company had released a free security patch for users to install if they are using the previous versions of Internet explorer including IE 7, 8 and 9.

"We're aware of targeted attacks potentially affecting some versions of Internet Explorer," Microsoft said in a statement. According to Rapid7, a security company, the bug can exploit computers running Windows XP, Vista and Windows 7.

The IE was infected by“zero- day” vulnerability, which according to the researchers is very hard to find. They are rare and require highly skilled hackers or software engineers to spend lot of time to analyze the code for security holes and launch the attack. In 2011, security researchers were able to discover only eight major zero day vulnerabilities.

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The bug was discovered after Eric Romang, a researcher in Luxembourg found his PC infected by a piece of malicious software known as Poison Ivy. It is used by hackers to steal data or take remote control of PCs. On further analysis, he found that Poison Ivy had gotten on to his system by exploiting a previously unknown bug, or zero-day vulnerability, in IE.

Considering the widespread use of IE by hundreds of millions, Microsoft had responded quickly, offering a free security patch.

Internet Explorer is used to be the most widely used browser in the world untill Google Chrome overtook it back in May 2012.