The criteria for universal network-level call blocking are as follows:
- The caller ID for international originated calls with less than 3 digits or exceeds 15 digits.
- The caller ID contains a number that does not conform to a valid format under the NANP. For example:
- Numbers that are not 10 digits (exception for 7 digit numbers such as 310-XXXX)
- Calls coming from a single number (111-111-1111)
- Calls coming from invalid area codes
- Calls with numbers that have a 0 or 1 in the 4th position of the telephone number i.e. 613-012-1234
- Calls matching the telephone number of the person being called.