http://www.dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/w/index.php?title=Dev/Leak_Tests&curid=264&oldid=83683
Monitor incoming connections to own server. This leak test while interesting might not catch all types of leaks such as DNS leaks. If source-available: Review the application source code. If closed source: Avoid Non-Freedom Software or reverse engineering.