An extensive physical examination of the telephone instruments must be undertaken. The newer, electronic telephones have other vulnerabilities, some of which are simple system features which can be abused. After the instrument is inspected, it is put back together and its screws are sealed over with friable security tape, thus providing visual proof that the phone has not been opened since the last inspection. A good consultant will have these seals custom made so that they can not be easily duplicated. Executives and security personnel may periodically inspect these seals themselves.
Broken seals indicate an intrusion, while missing seals indicate a switch of telephone sets.
Treat either condition as a suspicious incident. Inspection of Telephone Wiring. Wiring associated with the telephones under test are inspected for attachments, and damage. Damaged wiring is often the only evidence of a prior wiretap. Inspection of Junction Blocks.