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Ask HN: How do scammers spoof real phone numbers?

by gigapotential on 7/10/24, 11:05 PM with 6 comments

I got scam call from a number listed on USPTO website. How do they spoof a real phone number? What tech enables them do so?

I recently was targeted by this scam: https://www.reddit.com/r/Patents/comments/15yktus/called_by_uspto_scam/

  • by 486sx33 on 7/11/24, 2:39 AM

    How does someone do this these days for spam calls? You can just program your VOIP system to use ANY phone number for caller id. The VOIP system in my corporation can even do this PER EXTENSION and update each second if you write a simple script to interface with the web interface. Most phone systems even support additional character transmission like I could call you from my VOIP and it would say 800-288-4727 x 2600 (or anything I desire!)

    There is literally no security to it at all

    Basically the caller ID info is transmitted between the 1st and 2nd ring. If further caller ID data is transmitted after (like the real data), it is ignored

    If your data gets to the receiver first, it gets displayed

    It’s been possible to “spoof” caller id since forever, and there were open descriptions of the process and methods of generating that data and transmitting it since at least 1998. I can recall a popular electronics article on this with circuit layout.

    This is probably similar and would require flashing the chip with the included .asm file… https://www.elektronika.ba/385/caller-id-and-ring-generator/

    Click the red download button, I’m not able to grab the zip file link directly from my iPhone but it does download and show the circuit diagram

    Someone here would have the skills to closer examine the .asm if they were well versed in atmel chips , specifically AT90S1200 This would be for use with an old fashioned POTS phone line. But hey this is hacker news I thought someone might be interested in the analog option :)

  • by themerone on 7/11/24, 12:30 AM

    The SS7 protocol that transmits caller id info was developed when there was only one phone company in the United States. There was zero consideration to security. Nobody needed to consider what happens if a bad actor is added to the SS7 network, because the only connections were between national phone networks.

  • by toast0 on 7/12/24, 2:35 AM

    T1 digital calls have a field for outgoing caller ID. Voip to voip digital calls have a field for outgoing caller ID.

    Stir/shaken provides a path to validated caller ID, but the industry is not far enough down the path that unvalidated caller IDs can be dropped.