Don't gossip about sensitive people or projects on the telephone. Keep a pad and pen next to the telephone. Jot down details of threatening or suspicious calls immediately. Note the time, date and keep a file. Don't waste time worrying about phone taps or imagining that strange clicks or hums or other noises indicate a phone tap.
Many taps are virtually impossible to detect.
Trust your instincts. If you think your phone is tapped, act accordingly. Be aware that the United States Post Office will give your street address to inquirers under certain circumstances. If you receive a threatening letter, handle it as little as possible. Put both the letter and the envelope in a plastic bag or file folder.