Microsoft has urged hundreds of millions of Internet Explorer users to download security software after a newly discovered bug makes PCs vulnerable to hacker attacks.

The browser's security flaw enables attackers to exploit the bug, infecting the PC of users who visit a malicious website as a result.

But the software giant has advised customers to install the free security tool, named Enhanced Mitigation Experience Toolkit (EMET), through an advisory on Microsoft's website.

Microsoft says the move is an interim measure to combat the bug, with the software needing to be download, installed and then manually configured to offer protection to computers potentially at risk.

Users were also advised to adjust several Windows security settings to fight the threats but warned such actions could impact on PC usability - which at present seems a small price to pay for computer safety.

Some security experts, however, believe it would be easier for Windows users to temporarily jump browser ship so to speak, instead using rival systems such as Google Chrome or Mozilla Firefox.

To access the software click here.