Fighting against FAS¶

FAS (Fake Answer Start) - indication to caller about call answering, while dialed subscriber hasn't actually picked up the phone.
This is one of fraud schemes, often used in contemporary world of telecommunication.

• the outbound call towards dialed subscriber is in progress (call is directed to subscriber, but he hasn't picked up yet)
• the outbound call towards dialed subscriber is not yet dialed (but will be dialed a bit later)
• the call is not directed to dialed subscriber at all (audio file or ring-back tone is played back, or call is directed to call-center, where the task of operators is to hold a caller as long as possible)

This gives a chance to such a provider to send you overrated invoices.
During this kind of fraud it's obvious that caller suffers the most.
Unscrupulous providers could insert such FAS calls inside a call stream randomly.
Thus, it's hard to detect such calls.

To fight against FAS following methods are used:

• Provider testing
• FAS-Detector

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