VoIP hacks gut Caller I.D.

Via SecurityFocus HOME News

According to the article, using 'the open-source Linux-based PBX software Asterisk, used in combination with a permissive VoIP provider' can be used to fool caller id, and even get caller numbers that are supposed to be private." But don't blame the messager, the system has long been open to manipulation.

See more about Asterisk here and here

Update : Om a related item Caller ID Falsification Service