Skype investigates tool that reveals users' last known IP addresses

Skype said Tuesday it is investigating a new tool that collects a person's last known IP address, a potential privacy-compromising issue.

Instructions posted on Pastebin on Thursday showed how a person's IP address could be shown without adding the targeted user as a contact by looking at the person's general information and log files.

Skype, which is owned by Microsoft, said that "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 taking measures to help protect them".

In October, Skype acknowledged a research paper that showed how a Skype user's IP address can be determined without that user knowing. It also demonstrated that more than half the time the IP address could be accurately linked to sharing content using the BitTorrent file-sharing protocol.

An IP address is an important piece of information that can be used to track the approximate location of a user and their service provider. But the information is not necessarily accurate, as a person could be using a VPN, whose data center may be located in a different country than the actual user.

Another way to broadcast inaccurate IP addresses is browsing the internet using The Onion Router (TOR), an anonymising service that routes a person's internet traffic through a network of worldwide servers in a fashion that is difficult to trace. An IP address also just identifies a computer and not the person sitting behind a keyboard.

Skype uses a peer-to-peer system to route its data traffic, which is also encrypted. But its encryption system is proprietary and not been open for scrutiny, which has prompted caution from security experts.