$ sudo tcpdump -An "tcp" | grep "www"
listening on pktap, link-type PKTAP (Apple DLT_PKTAP), capture size 262144 bytes
.............". ...www.odezz26nvv7jeqz1xghzs.com.........
.............#.!...www.bxbko3qi7vacgwyk4ggulh.com.........
.6....m.....>...:.........|../* Z....W....X=..6...C../....................................0...0..0.......'....F./0.. *.H........0%1#0!..U....www.b6zazzahl3h3faf4x2.com0...160402000000Z..170317000000Z0'1%0#..U....www.tm3ddrghe22wgqna5u8g.net0..0..
A network observer could run a DNS lookup on the hostnames and see if they are real or not. So my idea would be to register a set of random hostnames which are legitimate and point the IPs somewhere to avoid looking for an NX Domain response and dropping the stream. You could even give each relay a unique subdomain and rotate these every few weeks. This may be expensive to implement but could make blocking Tor traffic with this method harder. Thoughts?
Cordially,
Nathaniel Suchy