Why scammers call you and say nothing - and how to respond safely

Source: ZDNet

Thawatchai Chawong/iStock / Getty Images Plus via Getty Images

ZDNET’s key takeaways

• There’s a reason scam callers don’t respond 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 greeted with silence? Sometimes, no one responds at all. Other times, there’s a short delay before someone finally greets you. You may think the person on the other end is just confused or distracted, or possibly got the wrong number. But that’s not the case, at least not with a scam call.

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What do scammers then do with your number?

“Calls where 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 at industrial scale, and before they invest human effort in a target, they validate that a number is active and answered by a real person.”

“In modern fraud ecosystems, verified contact data has value,” Barney said. “It is bought, sold, and reused. A silent call can serve as a filtering mechanism, separating dormant numbers from reachable individuals. 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, your confirmed number may lead to phishing calls or emails. In other instances, you might be the target of a more serious type of attack.

“Once that validation occurs, it strengthens the attacker’s ability to execute more convincing follow‑on attacks,” Barney said. “A confirmed number can be paired with a breached email address, used to trigger password‑reset flows, or targeted for SIM‑swap fraud.”

These types of scams are nothing new, though they were more prevalent years ago, Barney explained. They seemed to go out of style as email and SMS phishing attacks became more common. Seeing them resurface highlights an important aspect of cybercrime: attackers will reuse tactics and techniques that work.

What about calls in which the person responds after a short delay?

“That pause is typically a function of predictive‑dialing infrastructure,” Barney said. “These systems place high 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.”

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How to handle these types of calls

1. Hang up – If it’s an unknown number and no one responds to your greeting, just hang up. The only downside is that some calls with that initial silence may be legitimate (e.g., an office or known company). In that case, they will usually call back and may leave a voicemail.

2. Don’t respond, but stay on the line – Pick up a call from an unknown or suspicious number, but say nothing. If you hear only silence, wait to see if the call disconnects. If the spammer doesn’t detect a voice, they may mark your number as inactive and remove it from their list.

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3. Use spam‑call filtering – iPhones and Android phones have built‑in ways to block and identify spam calls, but a dedicated spam‑filtering app or service provides more granular control. In the US, the three major carriers—Verizon, AT&T, and T‑Mobile—offer their own tools for dealing with spam calls. You’ll also find a variety of third‑party spam‑filtering apps. Some apps to con

The callers are RoboKiller, Truecaller, and Hiya.