Why Do Phones Often Ring Once and Then Hang Up? Experts Reveal the Hidden Purpose: 'Never Call Back' — Saying a Word Can Be Disastrous, and Answering Gets Very Complicated

Have you ever frequently encountered strange calls that ring just once and then hang up, or where the caller goes completely silent the moment you answer? Don’t assume it’s just a wrong number! Cybersecurity firm Trend Micro, the popular anti-scam app Whoscall, and Dr. Shu-Cheng Yang, Chair of the Department of Information Management at National University of Kaohsiung, jointly warn that such unknown calls are common "reconnaissance tactics" used by scam groups and unethical marketers. Behind them lie four major cybersecurity and financial risks. If you accidentally answer or call back out of curiosity, you could become a target for scams.

The Hidden Dangers of "One-Ring and Hang Up" Unknown Calls: Experts Reveal Four Dark Traps Behind Scam Groups

According to cybersecurity experts and anti-fraud teams, these mysterious calls, mass-dialed by automated "number screening machines," primarily serve four purposes:

1. Testing Number Activity (Cleaning Active Number Lists)

Scam groups use systems to dial numbers en masse. If you answer or call back, your number is marked as an "active, in-use number." You will immediately be tagged as a "responsive target," potentially facing a flood of promotional SMS messages or scam call spam.

2. Luring Call-Backs to Earn High Call Charges

Scammers often use international codes with a '+' prefix (e.g., +882, +216) or special high-fee numbers, ringing just once before hanging up. If you call back out of curiosity, the call connects instantly to a high-fee international voice system, resulting in astronomical phone bills.

3. Collecting AI Voiceprint Samples

Some "silent calls" that go quiet after connection may aim to record the victim’s voice when they answer—such as "Hello?" or "Hi." As AI technology advances, these voice samples could be used for deepfake voice synthesis, enabling sophisticated voiceprint scams.

4. Luring Users to Click Malicious Links and Leak Personal Data

Some phishing calls, after the user calls back or answers, use voice guidance to prompt actions—such as clicking SMS links or visiting specific websites—to steal personal information or trick users into installing malware.

What to Do When Receiving Mysterious Calls? Experts Share 3 Defense Strategies

Facing relentless spam and scam numbers, cybersecurity experts recommend the following practical solutions:

1. Strictly "Do Not Answer, Do Not Call Back"

For unknown numbers, especially international calls starting with '+', simply ignore them. Never call back out of curiosity.

2. Use Caller Identification Tools

Install anti-scam apps like Whoscall or Trend Micro’s AI Anti-Scam Expert to receive real-time alerts and filter out most spam and scam numbers.

3. Utilize Built-in Phone Filtering Features

iPhone users can leverage the built-in "Silence Unknown Callers" feature in iOS. This requires unknown callers to provide information before ringing, effectively blocking silent calls and number-testing attempts.

Finally, if you suspect you’ve encountered a scam or have concerns, immediately call the 165 anti-scam hotline for consultation. A little more vigilance can protect your finances and personal data.