Skype privacy vulnerability

[silicon_toad2000]

A Skype user's IP address can be figured out even without their knowledge due to a major privacy vulnerability, the researchers wrote. Skype was notified in May -- the same month that it was announced Microsoft had acquired the company -- but the issue has not been fixed...
...The researchers built a Skype tracker that selected a set of 100,000 identified users. To correlated those IP addresses with files shared on BitTorrent, they also built tools to collect BitTorrent file identifiers, called infohashes, a BitTorrent crawler to collect IP addresses on the network and a verifier to match an online Skype user with an online BitTorrent user.
"As soon as the BitTorrent crawler detects a matching IP address, it signals the verifier, which immediately calls the corresponding Skype user and, at the same time, initiates a handshake with the BitTorrent client," they wrote.
A Skype user and a BitTorrent user could appear to be one and the same because they have the same IP address, but that may not be true due to the use of NAT (Network Address Translation), which allows several machines to share one public IP address. To weed out false positives of this nature, the researchers looked at identifiers in the IP datagrams received to see whether they had been sent shortly after one another from the same machine. If the identifiers in the datagrams generated by Skype and BitTorrent suggested they were sent close together in the same sequence, the Skype user was likely to be the one using BitTorrent...
...Using information that users publish in Skype's directory, such as their name, location, and birth date, the researchers were able to get very close to identifying the person doing the sharing. They note, however, the method will just identify a machine rather than an actual person behind the computer.

PCWorld article here

research paper here