Microsoft has warned of a vulnerability in its popular Windows software that is being exploited by a Russian hacking group suspected of attacking U.S. political institutions this year.

The software maker said in an advisory on its website on November 1 that there have been a small number of attacks using "spear phishing" e-mails from a hacking group called Strontium, also known as Fancy Bear or APT 28.

Microsoft's disclosure of the new attacks linked to Russia came after Washington accused Moscow of launching an unprecedented hacking campaign this year aimed at disrupting and discrediting the upcoming U.S. presidential election.

The U.S. government last month formally blamed the Russian government for the election-season hacks of Democratic Party e-mails and their subsequent disclosure on WikiLeaks and other websites. Russia has denied those accusations.

Microsoft said a patch to protect Windows users against the newly discovered threat will be released on November 8 -- election day.

More at RFERL.