Abstract:
The document is a project work on study of call toll fraud. It presents a method of detection and
prevention/mitigation of toll fraud in VoIP PBX infrastructure. The method is based on
measuring call setup delay time, of which the measured time is used to calculate the fixed
distance between the calling and called directory numbers. Distance cannot be spoofed like IP
addresses or directory numbers, hence an alternative method to detect toll fraud. A lookup table
built during initial installation provides radial distances (times) for local, national and
international calls’ destinations. A comparison between measured and threshold set values
classifies normal and fraudulent calls. The document also provides a method for monitoring long
duration calls. In this approach when a set threshold is exceeded, that call is suspicious, and is
classified as a fraudulent call. In both techniques, a fraud call is disconnected and the same
reported to the administrator.
Cyber criminals use brute force or else to get the PBX credentials. Once access allowed, they
hijack the system and make it their call center. This crime is currently making businesses loss
billions of money to fraudulent callers who make/re-sale calls without paying. VoIP is a new
technology and its proper use has many benefits on national development of a country. The
importance of VoIP services motivated the us to study the mentioned methods above.
