The number of robocalls being made every month is staying pretty much the same, and individuals who answer robocalls are not more likely to get more of them than people who do not answer robocalls, are two of the conclusions reached by researchers from North Carolina State University, who analyzed 1.5 million robocalls sent to more than 66,000 phone lines they set up.
The researchers recently won an Internet Defense Prize from Facebook and their work was recognized as a Distinguished Paper at a security symposium held last week.
Working with Bandwidth.com, the researchers set up more than 66,000 phone lines for the purposes of monitoring them for robocalls. During an 11-month period in 2019 and 2020, the lines received nearly 1.5 million calls, of which 146,000 were answered and recorded. The group defined a robocall as “an automated or semi-automated calls that play a recorded message.”
The number of calls received by the researchers’ phone lines were nearly identical from month to month, and whether a robocall was answered or not had no bearing on whether that line received more calls in the future.
One problem that the researchers did identify is what happens when a robocaller uses someone’s actual phone number to place its calls. Many of the people who see the missed call on their phone call that number back, making it impossible for the person who owns that number to use his or her phone, which can last for a day or two, the researchers noted.
Nearly two-thirds of the calls that were answered and recorded contained no audio or sound from the caller, and only half of the remaining calls contained enough audio to conduct an analysis.
Weeding those calls out, though, allowed the researchers to begin to identify clusters of calls into specific campaigns, which could then be tracked down.