Microsoft is investigating reports of a vulnerability that can enable an attacker to determine the IP address of a Skype user. But according to a report, Skype has known about IP leak issues since late 2010.

According to a report in The Wall Street Journal, Skype was told about an IP tracking vulnerability more than a year ago, but has left the situation unpatched. The Journal reported that researchers from Inria, a research institute in France, and the Polytechnic Institute of New York University shared their findings about the vulnerability in November 2010. Their research was published in October 2011 -- the same month that Microsoft finalized the Skype acquisition -- and demonstrated how to secretly track the city-level location of 10,000 Skype users.

The researchers found that they were able to uncover the IP address of Skype users as well as their city locations by making a masked call to a user. Once the call was made, the researchers obtained the IP address from information Skype automatically sends to the caller. In their experiment, they found that by repeating a call every hour, it was possible to map a user's movement to see if they moved from city to city.

Research team leader Stevens Le Blond told the Journal he re-tested the findings after reports circulated during the past several days about information posted on Pastebin regarding another way to get user IP information from users running a patched version of Skype 5.5.

"We are investigating reports of a new tool that captures a Skype user’s last known IP address," says Adrian Asher, director of product security at Skype, in a prepared statement in response to the situation. "This is an ongoing, industry-wide issue faced by all peer-to-peer software companies. We are committed to the safety and security of our customers and we are takings measures to help protect them."

"By calling it a 'new tool' it means they don't have to respond as urgently," Le Blond was quoted as saying by the Journal. "It makes it seem like they just found out."

The company declined to answer questions about whether the issue has been exploited yet.

Knowledge of this situation is critical for those who use Skype in situations where locations need to be kept secure, as well as for those concerned with their privacy, opines Nick Furneaux, managing director of U.K.-based CSITech, in a blog post about the issue posted on Pastebin.

"I've tested this and it does what it says on the tin," he wrote. "I was able to extract the external and internal IP's of a friend in the US to within a few miles of his house, a buddy in Asia to within a few streets and my own to just a few miles down the road. More concerningly [sic] the internal IP combined with the internet facing address provides the basis for a direct probe and then attack of any individual on Skype's global address book."

*This story was updated with additional information.

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