How to identify a spam call: the signs that give it away

You get a call from a number you don't know, you pick up and there's only silence. Or maybe a voice rushing you to sign up for something "before the day is over". These situations follow a pattern, and learning to read it is the best defence against phone spam, scams and robocalls.

In this guide we go over the specific signs that give away an unwanted call and, above all, how to check a suspicious number before doing anything.

The signs that give away a spam call

No single sign is conclusive on its own, but when several pile up, the odds that you're dealing with a junk call shoot up.

They call at odd hours

Legitimate telemarketing usually respects business hours. A call first thing in the morning, at lunchtime, very late at night or on the weekend is suspicious. Mass automated campaigns don't account for your time zone or your habits: they simply dial.

Unknown, hidden or international number

Be especially wary of:

• Numbers you haven't saved and weren't expecting.
• Calls with a hidden or private number: someone with something legitimate to tell you rarely hides.
• International prefixes you don't recognise. A missed call from a country you have no connection to is usually a wangiri ("one ring") scam: they call, hang up and wait for you to call back a premium-rate number.

If you're unsure about the geographic origin, check our prefixes guide to place where the number comes from before reacting.

Silence when you answer: the fingerprint of the auto-dialler

One of the clearest signs: you pick up, say "hello?" and on the other end there are a couple of seconds of silence before a voice comes in, or no one answers at all and the call drops.

That's an auto-dialler (robocall). The system launches calls en masse and only connects an agent when it detects that someone has answered. That delay is the time the system takes to pass you to a free person. If no one ever speaks, it means there was no agent available: your number only served to confirm the line is active.

Pressure and a sense of urgency

Scams and aggressive telemarketing run on artificial haste:

• "This offer expires today."
• "Your line will be suspended in the next few hours."
• "There's a suspicious charge, I need to confirm your details now."

The goal is to make you act without thinking. A serious organisation never demands immediate decisions over the phone.

They ask for personal data, passwords or payments

This is the red line. No bank, public administration or legitimate company will ask you over the phone for:

• Passwords or verification codes (the famous one-time SMS codes).
• The PIN or CVV of your card.
• To install an app to "fix a problem".
• An immediate payment by transfer, cryptocurrency or gift cards.

If they ask you for any of these things, hang up. It's not a conversation worth continuing.

Suspicious prefixes and patterns

Some numbering ranges are associated with commercial campaigns or premium rates. Spoofing is also common: the scammer fakes the number that shows on your screen so it looks local or even identical to your own bank's. That's why the number you see does not guarantee who's really calling, and it's worth verifying on your own.

How to check a number before calling back

The golden rule: don't call back on impulse. Investigate first.

1. Search for it online. Paste the number into a search engine. If it's known spam, chances are other people have already left warnings.
2. Look it up in a reports directory. A community service tells you at a glance whether a number is racking up complaints. Check the spam numbers directory to see if other users have flagged it and why.
3. Find out who's behind it. If you want to go a step further, our guide on who's calling you explains how to trace the origin of an unknown call.
4. Check the prefix. A number with a geographic prefix that doesn't fit, or an unexpected international one, is reason enough not to call back.
5. Verify through the official channel. If they claim to be your bank or an administration, don't use the number that called you. Hang up and call the number listed on your card, in your contract or on the official website.

What to do about a suspicious call

If you're already getting the call or have just hung up, act like this:

• Don't give out any data or confirm personal information, not even your full name.
• Don't follow instructions to press keys, install apps or "verify" your identity.
• Hang up without explanation. You don't have to justify yourself to an unsolicited call.
• Don't return missed calls from international numbers you weren't expecting.
• Note the number and the time, in case you need to report it or document a pattern.
• Block the number to avoid future nuisance. We explain how in block spam calls.
• Report it. Every warning helps the next person get a heads-up in time.

If the call went further and you think you may have given away sensitive information, follow the steps in our guide on what to do about a suspicious call to limit the damage.

Summary: your three-second mental checklist

Before following any unexpected call, ask yourself:

• Do I know the number or was I expecting it?
• Was there an odd silence when I answered?
• Are they rushing me?
• Are they asking for data, passwords or money?

If any answer sets off an alarm, hang up and verify. Phone spam relies on your quick reaction; your best tool is to slow down by one step.

Check and report the number

Just got a strange call? Don't be left wondering. Search the number in NoCall's spam numbers directory to find out instantly whether other users have flagged it, and report your case to protect the next person. Together we make sure robocalls have fewer and fewer places to hide.