Voice over Internet Protocol service
has become very popular since the last two decades, but is vulnerable to many
types of fraudulent activities. False Answering Supervision or FAS is one of
the well known VoIP fraud of incorrectly extra billing the customers.
What is FAS?
To explain FAS simply, it is the
scenario when after making a call, the caller gets billed also for the time the
call is not answered. There are three main types of FAS.
·
The carrier returns the answer signal
when ringing starts, rather than when the customer answers. This increases the
duration of the call, and therefore the cost of the call. A call may even be
charged despite being dropped due to no answer.
·
The more clearly fraudulent variant of
this scheme involves call diversion. The fraudulent carrier will route the call
to a recorded message that plays a ringing tone and then a recording . This is
intended to keep the calling customer on the line and paying for the call as
long as possible.
·
The call is not terminated when the
recipient hangs up, and waits for the caller to disconnect. During the period
between the recipient disconnecting and the caller disconnecting, the caller is
billed.
How to identify FAS?
If the customer notices any of the
the following, then it is pretty obvious that there is FAS problem.
·
The billing time is longer than the
time for which the called party was available on the line.
·
The call is billed even if the called
party is out of the coverage area.
·
The call is billed even if the called
party is not available and the caller gets a voice mail.
Why FAS occurs?
FAS generally takes place if no
synchronization is there between the VoIP leg and the PSTN leg of a call on a
VoIP-to-PSTN gateway. When the call reaches the gateway from the VoIP network,
the gateway tries to establish a connection with the called number, but due to
incorrect configuration it cannot detect the states of the call, which are
advertised by the PSTN network (the states are: "called party
ringing", "called party connected"). And thus the gateway forces
the "CONNECT" state and it normally happens immediately after the
arrival of the call from the VoIP network or a few seconds after that. But the
main idea is that the gateway connects the calls (which means starts the part
of the call, which is billed) according to its own settings, but not according
to the actual state of the call.
How FAS works?
The FAS server is placed into the
routing of the switch. Now the calls that come to the FAS server will be
forwarded to an IVR message, related to the dialed number. The message that
will be played back will sound something like this: "the subscriber is out
of reach, please, try to call later" (it depends on what message is
recorded on the FAS server) but this message should be exactly the same as the
caller would get from the real carrier of called number. The call will be
billed from the very beginning and this will be the billable time that will
generate additional profit.
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