[VoiceOps] Dead Air calls to TFNs

Ivan Kovacevic ivan.kovacevic at startelecom.ca
Tue Apr 14 10:31:16 EDT 2015

Over the last 3 months we have seen a marked increase in dead air calls to
Toll Free numbers that belong to us, our customers, etc.

If there is an answering machine on the other side, these calls result in a
dead air voice message of few seconds in duration. If a live person picks
up they won’t hear anything on the other side and the line stays connected
(didn’t measure for how long, but more than 60 sec). The volume varies
daily but ranges from 0 to 4-5 calls per day.

Calls come from US ANIs (925, 631 area codes for example), but ANI is
easily spoofed so doesn’t really mean much. In fact, when we called some of
the numbers we got private residences of folks who did not call us.

Other than the nuisance factor (our support line is getting the calls as
well) and a small additional cost there doesn’t seem to be a real impact.

Are these just war-dialling attacks to find back doors?

Is anyone else seeing the same? Are you doing anything to prevent it?

Best Regards,

Ivan Kovacevic

Vice President, Client Services

Star Telecom | www.startelecom.ca | SIP Based Services for Contact Centers
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