German engineer Arthur Scherbius filed patents for the Enigma rotor cipher machine, aiming to secure commercial and diplomatic telecommunications against wiretapping and line interception.
Astronomer Clifford Stoll traced a 75-cent accounting error at Lawrence Berkeley Lab to a hacker in Hannover, Germany using international X.25 network gateways to spy for the Soviet KGB.
Karsten Nohl and the Chaos Computer Club published a 2-terabyte rainbow-table set at 26C3 enabling real-time over-the-air decryption of A5/1-protected 2G GSM calls and SMS with inexpensive hardware.
Sylvain Munaut and Harald Welte demonstrated OsmocomBB at 27C3, releasing an open-source GSM baseband stack that enabled over-the-air call decoding on $15 consumer handsets.
Tobias Engel and SRLabs demonstrated at 31C3 that SS7 design flaws allow global subscriber location tracking, call interception, and SMS 2FA theft using legally obtainable access to the signaling network.
Cybercriminals abused SS7 roaming interfaces to intercept bank-issued SMS one-time passcodes (OTPs), draining accounts of customers at O2 Germany and Metro Bank UK.