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ZDNET Highlights
- There’s a reason scam callers don’t answer when you answer.
- The goal is simply to confirm that your number is active and spammable.
- To deal with a call, hang up and use spam filtering to block them.
Have you ever answered a call from an unknown number only to be answered with silence? Sometimes no one answers at all. Other times, there’s a slight delay before someone finally welcomes you. You may think the person on the other end is simply confused or distracted, or possibly got the wrong number. But that’s not the case, at least not with scam calls.
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Yes, there is a method behind this madness. Just knowing that someone answered the call is confirmation that the phone is owned by a real person and the number is active. This marks the intended victim and number available for future scams.
“Calls to which no one responds are rarely accidental,” Shane Barney, chief information security officer at cybersecurity provider Keeper Security, told ZDNET. “In many cases, they are automated reconnaissance events. Fraud operations run on an industrial scale, and before investing human effort into a target, they verify that a number is active and answered by a real person.”
Then what do scammers do with your number?
“In the modern fraud ecosystem, verified contact data has value,” Barney said. “It is bought, sold, and reused. A silent call can serve as a filtering mechanism, separating inactive numbers from reachable persons. It is less about the conversation and more about confirming that there is someone on the other end.”
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In some cases, phishing calls or emails may come from your confirmed number. In other cases, you may be the target of a more serious type of attack.
“Once that verification is done, it strengthens the attacker’s ability to carry out more concrete follow-up attacks,” Barney said. “A confirmed number can be associated with a compromised email address, used to trigger a password reset flow, or targeted for SIM swap fraud.”
Barney pointed out that these types of scams are nothing new, although they were more prevalent years ago. As email and SMS phishing attacks became more common, they fell out of favor. Seeing them resurface highlights an important aspect of cyber crime. Attackers will reuse strategies and techniques that work.
What about calls in which the person responds after a slight delay? It talks about automated operations run by spammers and scammers.
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“That pause is generally a function of predictable dialing infrastructure,” Barney said. “These systems place large volumes of calls simultaneously and use algorithms to detect when a human answers. Once a voice is detected, the system routes the call to a live operator. The delay reflects the handoff process. From an operational standpoint, this model allows scammers to maximize efficiency while minimizing labor costs.”
With all this in mind, how should you handle these types of calls? Here are three tips.
hang up. If it’s an unknown number and no one answers your greeting, simply hang up. The only downside here is that some calls with initial silence may appear legitimate, perhaps from an office, business or known company. In that case, they will call back and may let the call go to voicemail. If it’s important, the person will leave a message.
Don’t respond, but stay on the line. Another strategy is to pick up the call from an unknown or suspicious number, but don’t say hello or anything else. If you hear nothing but silence, just wait to see if the call disconnects. If the spammer or scammer does not hear from the other end, they may consider your number inactive and remove it from their call list.
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Use spam call filtering. iPhone and Android phones have built-in ways to block and identify spam calls. But a spam filtering app or service offers more detailed control. In the US, the three major carriers – Verizon, AT&T, and T-Mobile – offer their own tools to deal with spam calls. You’ll also find a variety of third-party spam filtering apps. Some apps to consider are robokiller, truecallerAnd Hiya.
