February 27, 2013

How Phone Spammers Find Your Phone Number

If you have suffered from spam SMS or telemarketing calls, here is how phone spammers find your phone number.

Automated Phone Number Verification Tool

WebRoot discusses how phone spammers find your phone number using automated tools. 

An example is an automated phone number verification tool offered by a Russian vendor (screenshot above) – 
The first version of the tool will basically take advantage of a single USB modem, and will automatically attempt to “blank call” a given list of phone numbers, successfully differentiating between a “free line”, “busy line” and “non-existent number” type of results. In order to speed up the process, the second version of the tool allows the use of multiple USB modems to achieve the same objective.
Using the automated tools spammers can verify large quantity of mobile numbers quickly. Once a phone number is found to be valid, then it is on their list to send spam SMS or automated telemarketing calls.

FTC’s robocall blocking challenge is looking for solutions to block such automated sms and calls. Many of the solutions offered require routing your calls through an intermediate service which can set rules to filter out these automated calls – e.g. these challenges based filtering methods.

The best solution is for carriers to offer free tools to help filter out these sms/calls, much like email filters from your mail provider, but the carriers are unlikely to provide that.


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