netresec

Yes. Sorry for the confusion. The original tweet has now been removed and a correction has been posted instead.

We first tried to post replies with corrected information, but it didn't seem to help. The tweet has now been deleted and a correction tweet has been posted instead.

The PCAP in the referenced tweet was created using PolarProxy, which decrypts and re-encrypts TLS traffic while saving the decrypted traffic to a PCAP file.

MitM'ing the traffic using a trusted root CA allows TLS traffic to be decrypted, even if perfect forward secrecy is used. That's what we did to produce the decrypted PCAP shown in the Wireshark screenshot.

You are completely right. The traffic was sent as TLS encrypted HTTP/2 traffic to Microsoft. We decrypted it using PolarProxy in order to see what was transmitted. The screenshot in the tweet shows the decrypted PCAP generated by PolarProxy.

You are correct. This traffic was not generated by typing text into the "run box", it was generated by typing text into the "start menu box". We are very sorry for the confusion this has caused. The wireshark screenshot shown in our tweet was showing TLS traffic that has been decrypted by PolarProxy. That’s why it shows up as HTTP/2 traffic over TCP port 80.

The purpose of the "Great FIrewall of China" is to censor the Internet, i.e. the intention of this MITM doesn't seem to be to covertly spy on the University user's searches.

A self signed X.509 cert is enough in order to see what they are searching for and to block/RST queries for topics like "Tiananmen Square protests". The CH authorities don't care if users notice the MITM in this case.