Speaking on Deep Background, the Press Secretary whispered:
I'm told that most CALEA warrants only authorize a pen register, not an actual tap. Pen registers are trivial to implement, since the provider's software undoubtedly has an option to produce CDRs for billing or planning purposes. Unfortunately this doesn't cover the case of purely P2P calls which don't have a VoIP provider; if the suspect is using such software, the only way to produce a pen register is with a tap.
Note that the requirements for a trap/trace aka pen register are a fraction of those for a Title III intercept. See http://www.usenix.org/events/sec01/eckenwiler/index.htm for at least an introduction.. -- A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433