Caller ID

Caller ID is the service that displays the caller's number on the recipient's handset between rings. On SIP lines, this information travels in standardized headers of the same name; in VoIP it's easy to declare, and therefore easy to fake — that's spoofing, behind a large share of fraudulent calls.

For a local business, caller ID cuts both ways. Inbound: most people no longer answer unknown numbers, so screen with a system that identifies your real clients. Outbound: your callback from an unknown personal mobile gets ignored half the time — call back from your business number, or better yet, follow your call with a text explaining who you are. Carrier spam filtering now relies on caller ID authentication to tell real businesses apart from spoofed numbers.