For various reasons, it may be necessary to block incoming calls from certain phone numbers. This applies, in particular, when recurring calls cause disturbance or annoyance; call blocking may then be the only way of getting some peace and quiet. Call blocking is technically possible at various different points: the telephone provider’s network, the subscriber’s own Internet access , the telephone system or the end device. When blocking calls, a distinction is made between so-called negative and positive lists. While negative lists only block specified phone numbers and permit calls from all other numbers, positive lists only permit calls from individual phone numbers. In the latter case, calls from all other phone numbers are automatically blocked. It is also often possible to block callers who hide/suppress their phone number.