Tor has become a tool of free expression in parts of the world where citizens can not speak freely against their government. Many use the anonymous Web network to share information and updates with the rest of the world via social networks like Facebook and Twitter. What happens then when one of those social networks blocks Tor?
That very question arose today when Tor users found that they couldn't connect to Facebook. Some reports made it sound like Facebook was intentionally blocking Tor. That was not the case. The Tor Project team said Facebook's automated systems that detect malicious activity were to blame for the blockade:
A number of users have noticed that Facebook is blocking connections from the Tor network. Facebook is not blocking Tor deliberately. However, a high volume of malicious activity across Tor exit nodes triggered Facebook's site integrity systems which are designed to protect people who use the service.
It shouldn't come as a surprise to learn that freedom fighters and dissidents aren't the only ones using Tor. A number of criminals and ne'er-do-wells also use the anonymous Web browsing service for everything from drugs to child porn. Activity coming from these parts of the network could have triggered Facebook's automated defenses.
At 2:30 p.m. EST, Tor access to Facebook was restored. At that time, the Tor Project team offered an update that better explained the situation:
Facebook's site integrity systems detected automated malicious activity coming from a significant number of Tor exit nodes. In order to protect people while we investigated the problem, access via these nodes was temporarily suspended. This issue has now been resolved and Tor access routes to Facebook restored.
It's good to know that Facebook wasn't intentionally blocking Tor, but the situation is a perfect example of how important anonymous online services are. Many people were rightly concerned that they would no longer be able to post pictures and other information on social media for fear of being arrested by their government.