Researchers Receive 1.5 Million Calls on Unknown Phone Numbers
Experts from North Carolina State University presented an intriguing report at the USENIX conference, sharing the results of an experiment focused on robocalls. For the experiment, the researchers created a massive telephone honeypot and managed 66,606 phone lines over 11 months (from March 2019 to January 2020). During this period, they received a total of 1,481,201 unsolicited automated calls. Notably, the honeypot phone numbers were never made publicly available.
On average, unwanted calls were received every 8.42 days, with most robocalls arriving in distinct waves that the researchers called “storms.” These surges occurred regularly at consistent intervals and appeared to be part of well-organized campaigns. Over the 11 months, the team recorded 650 such “storms.”
Interestingly, not all calls during these activity spikes were from robots; most callers turned out to be real people. The researchers believe this is due to caller ID spoofing tactics, where robocallers disguise their real phone numbers and impersonate actual individuals. As a result, when victims missed a robocall and later called back the spoofed number, they would end up reaching the honeypot numbers managed by the research team.
“Interestingly, one of our lab colleagues also became a victim of such a ‘storm.’ Hundreds of strangers bombarded him with calls, complaining that they had received calls from his number! Needless to say, he couldn’t use his phone for several days until the calls subsided,” the experts noted.
The research team recorded about 10% (around 150,000) of the robocalls they received, which were then analyzed to determine their source and content. Through this analysis, they identified 2,687 unique robocall campaigns. The largest of these promoted student loans, medical insurance, Google search ranking services, and social security scams.
Perhaps the most interesting finding from the experiment was this: after answering one and a half million robocalls, the researchers did not observe any overall increase in the number of such calls.
“The media and regulators constantly advise users to avoid answering calls from unknown numbers to reduce robocalls. Surprisingly, we found that answering such calls does not necessarily increase the number of future robocalls. Users should still be cautious when receiving calls from unknown numbers, but if you occasionally answer an unsolicited call, it doesn’t mean you’ll start getting significantly more robocalls in the future,” the authors concluded.