ChannelVision Magazine

tion solutions came on the market. These call analytics applications enabled sub - scribers to report robocallers. The applica - tions generated databases of these calling numbers with reputation scores based upon crowdsourced reports. Another type of robocall solution involves dynamic traffic analysis: software monitors and scores by calling/called number, trunk, lo - cation and other such attributes. When scores cross critical thresholds, the software identifies a potential robocall pattern and can act. When robocalls are identified, responses can be ei - ther to block the calls or divert them to voice - mail or an interactive voice response system, such as a voice CAPTCHA, for example. Robocallers responded to these methods with neighbor spoofing, using fake caller IDs including the telephone number of their target victims. Reputation service applications don’t work very well when the perpetrator spoofs a legitimate phone number with an otherwise good reputation. The telecommunications industry proposed a solution: caller authentication. The frame - work is called STIR/SHAKEN, and it enables service providers to vouch for the caller ID us - ing digital signatures that robocallers cannot spoof. Call authentication does not stop robo - calls, but by verifying caller ID, it makes call analytics much more effective. Effective robocall prevention uses both caller authentication and call analytics working together. TDoS threats & solutions At TransNexus, we’ve noticed an uptick in calls from businesses looking for protec - tion from TDoS attacks. Organizations get so many incoming calls that they can’t get to legitimate customer calls. It’s shutting down their business. Some of these calls are robocalls. A perpe - trator has programmed his auto-dialer to make lots of calls through sequential blocks of num - bers. When they hit a block of numbers used by a business, or a hospital, for example, the impact can be disruptive. Such organizations try to answer every call, and the volume of ro - bocalls is overwhelming them. We call these robocalls “inadvertent TDoS.” The perpetrator hopes that people will answer the calls so he can scam them out of something. There are also “deliberate TDoS attacks.” The perpetrator isn’t trying to scam his vic - tims. He’s trying to shut down their telephone service. We’ve helped several businesses that suspect TDoS attacks have been carried out by their competitors. The robocall solutions discussed above are also effective against inadvertent TDoS. Dynamic traffic analysis is effective against deliberate TDoS. The volume of calls and thresholds might be different, but the techniques work well for both robocalls and TDoS. Neighbor spoofing solutions The best solution to combat neighbor spoofing will be widespread adoption of call authentication using STIR/SHAKEN. Again, it does not prevent either robocalls or TDoS at - tacks, but it does make other prevention meth - ods more effective. In the meantime, TransNexus has devel - oped another technique that has successfully thwarted neighbor spoofing in certain situa - tions. It involves flexible blacklisting based upon the SPID or OCN of the inbound calling number. Here’s how it works: When a service provider originates a call from one of its customers who is calling an - other one of its customers, that’s an on-net call. The service provider will route that call within its network. It will not leave that network, transit external networks, then come back into the ser - vice provider’s network. With flexible blacklisting, the service pro - vider examines calls entering its network from external networks. If it sees a call where the calling number is one of its own, the service provider know it must be neighbor spoofing. It then can either block the call or divert it to voicemail or an IVR. This method has been very effective in preventing robocalls and TDoS attacks. TransNexus offers a complete range of solutions to protect telecommunications net - works from disruptive robocalls and TDoS attacks. These solutions have achieved re - markable results with our customers, trans - forming unhappy, frantic subscribers into happy users. o Donald St. Denis is product marketing manager at TransNexus. He can be reached at donald.stdenis@transnexus.com . CORE COMMUNICATIONS 46 CHANNEL VISION | March - April, 2020