A law that specifies it is illegal to tap, or capture communication, over wires.
The act applies to email, telephone conversations, and data stored electronically.
The law was first brought to attention after the Captain Midnight broadcast signal institution, where an electrical engineer hacked into the HBO (Home box office, a US TV network).
The ECPA extended government restrictions on wire taps (monitoring telephone or online communications) from telephone calls to include transmissions of electronic data by computer
A similar UK alternative: Investigatory Powers Act