With a certain registry key, the manipulated version of Skype will create a log file with information including other users’ external and internal IP addresses. These IPs can be retrieved simply by opening up a user’s profile with the Skype client. In a test conducted by The H’s associates at heise Security, the log file always showed the correct IPs – and when a user was logged in with multiple clients, the IP addresses for all the clients were visible.
The service uses a modified version of Skype’s SkypeKit SDK that is currently only available via BitTorrent, and Zhovner has put the necessary Python scripts on GitHub. In a post on Hacker News, Zhovner says that Skype has already banned his account, likely because of his experiments.