The attacks they want to carry out are inherently loud. They're attacking visits to well-known websites at scale in ways that require changing the response retu

The attacks they want to carry out are inherently loud. They're attacking visits to well-known websites at scale in ways that require changing the response returned when visiting those websites in a way that's trivial to detect (the websites should immediately redirect to the SSL version but the attack has to remove that redirect in order to modify the contents in malicious ways, regardless of the exact details of the modification or how sneaky they make it). There's no real way around that. It's easy to just scan the entire exit node list for nodes launching this attack if you know what sites they're targetting.