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But just having the major phone carriers onboard is not enough for caller-authentication technology to work optimally. Many Americans, particularly those who live in more rural areas, still have old-fashioned copper-wire landline phones, and their phone service providers are not fully digitized and thus cannot support STIR/SHAKEN.
That means there will be gaps in protection. As the major carriers become more impregnable, the “bad guys” will move to the more vulnerable old-school telecoms to make their illegal, unwanted robocalls, says Gerry Christensen, a telecom expert and CEO of Mind Commerce, a research company that specializes in phone systems and networking technology.