Shielding

Shielding is used to protect data from emanating out so that it can be intercepted, or prevent interference from getting in and corrupting data transmissions.  A Faraday cage can be used to prevent emissions and interference.
A Faraday cage prevents signals from emanating outside a room. It uses electrical features that cause RF signals that reach the boundary of the room to be reflected back. It can also provide shielding to prevent outside interference such as electromagnetic interference (EMI) and radio frequency interference (RFI) from entering the room.