Attempts to communicate telephonically by a mobile phone are detected. When an attempt is detected, an associated phone number is identified and transmitted to a server in order to glean corresponding security information. On the server, a database is maintained containing 1) phone numbers known to present potential security concerns and 2) descriptive security information concerning each of these phone numbers. The server receives phone numbers from mobile phones to check for security information, searches the database for received phone numbers, and transmits corresponding security information to the originating mobile phones. Security information concerning identified telephone numbers is received from the server by mobile phones. Responsive to the contents of the received security information, detected attempts to communicate telephonically are allowed to processed, blocked or otherwise processed.