A system and method for screening telephone calls to a subscriber telephone number comprises a screening list of telephone numbers assigned to suspect callers and rules defining when a telephone number will be added to or removed from the screening list or ‘greylist,’ and/or modifying a screening value to be assigned to a telephone number in the greylist. Data relating to calls is received from subscribers and processed, and the telephone number is screened in accordance with the rules, based on the screening value assigned to the telephone number and optionally a selected subscriber tolerance level. Subscribers may add any telephone number to a personal list of telephone numbers to be blocked (blacklist) or telephone numbers to be accepted (whitelist).