It was actually tor (the threat came from tor), and harvard 'found' him by constantly logging what connections were going to known tor entries from on campus. As it turns out he was one or possibly the only one using tor that morning from harvard.
Bruce outlines it that he certainly could have stayed tight-lipped (all evidence was circumstantial) but, nevertheless confessed as soon as they approached him.
I'm looking forward to when VPNs always throw up chaff traffic.
Mullvads DAITA (Defense Against AI-guided Traffic Analysis) is going into that direction[0] and Mullvad is one of the better providers. Tor also has some protections against this afaik and the upcoming nym vpn is also doing some traffic obfuscation [1]. But as the saying goes: Correlation Attacks are a bitch.
The first line on the landing page says:
"The world’s most private VPN 80% off today!"
Very intresting.
Correlation attacks are a bitch and i'm sure i'm on a shortlist already but calling a politician an idiot with a burner account made using a vpn should be fine.