The encrypted messaging app Signal has stopped responding to requests from Ukrainian law enforcement regarding Russian cyberthreats, a Ukrainian official claimed, warning that the shift is aiding Moscow’s intelligence efforts.
Russia was caught running a bunch of side channel and phishing attacks using malicious QR codes. Presumably signal could help track these patterns in terms of time and place, to help isolate where espionage activity was occuring.
Malicious QR codes were used to establish a separate device as a 'linked device' which would allow the attacker to receive and read Signal messages sent to and from the target