Microsoft has warned web users to be extra vigilant following the discovery of a series of bogus SSL certificates that could theoretically be leveraged by hackers to mount cyber attacks.
Microsoft issued the warning in an advisory on its TechNet security service, alerting IT managers the certificates could be used by hackers to perform phishing and man-in-the-middle attacks.
"The SSL certificates were improperly issued by the National Informatics Centre (NIC), which operates subordinate CAs under root CAs operated by the Government of India Controller of Certifying Authorities (CCA), which are CAs present in the Trusted Root Certification Authorities Store," read the advisory.
"The subordinate CA has been misused to issue SSL certificates for multiple sites, including Google web properties. These SSL certificates could be used to spoof content, perform phishing attacks, or perform man-in-the-middle attacks against web properties."
The issue affects all supported releases of Windows, though Microsoft is yet to see any clear evidence suggesting hackers are actively using the certificates. Microsoft said it is updating Windows Certificate Trust list (CTL) to remove the bogus certificates and prevent future exploitation by hackers.
Tripwire security researcher Craig Young recommended IT managers take a variety of protective steps while Microsoft works on the update.
"One of the best ways to protect users from this type of threat is through the use of pinned certificates. This is a deployment in which software is designed to require specific certificates, instead of allowing any certificate signed by a 'trusted' authority," he said.
"This practice is used in the Gmail app for Android, for example. Unfortunately this approach does not scale for general web browsing. To protect themselves from these kinds of incidents users may want to remove trust for regional certificate authorities that aren't needed in the user's locale."
The advisory comes mere days after Microsoft released its monthly Patch Tuesday security update. The update included a critical fix for Microsoft's popular Internet Explorer web browser.