Comment Recieved out of band, delivered inband (Score 2, Informative) 171
Calls originated over ISDN can send a caller ID number in the out of band signaling channel. The SS7 switching network relays both the ANI and the Caller ID, which are identical for calls from POTS lines (which do not have an out of band signaling path to the local office). The phone company can provide the ANI for a call if there is an allegation of caller ID spoofing. The owner of the ISDN line which originated the call could then be charged for caller ID spoofing. Calls originating outside the U.S. might be harder to investigate.
Caller ID is delivered in band to POTS lines. This might allow the originator to send phony caller ID information inband. However, the speech path forward may not be opened until the call answers, which would make things tricky for the spoofer.
Caller ID is delivered in band to POTS lines. This might allow the originator to send phony caller ID information inband. However, the speech path forward may not be opened until the call answers, which would make things tricky for the spoofer.