Signals intelligence, or Sigint, entails eavesdropping on communications systems. Radio transmissions, including those from cellphones, can be picked up by listening stations on the ground and in planes, boats, and satellites. Satellites may also pick up microwave transmissions. Communications traveling by cable can be detected either by sending covert operations teams ashore to tap land lines or by using a submarine specially equipped for tapping underwater cables. And traditional burglary, bugging, and bribery can allow intelligence agencies to break ciphers or bypass encryption entirely.