Number Spoofing – What It Is And What To Do

Emily Dye

Emily Dye

What is number spoofing?

Number spoofing has been on the rise lately. Nuisance callers and criminals use number spoofing by deliberately changing the Caller ID to either hide their identity or mimic the identity of a real company or person.

Your calling line identity – or CLI or Caller ID – is the number that is presented to others when you call.  It’s really useful for screening calls and only answer the ones you want to.

These identity thieves and fraudsters often pose as representatives of organisations you do business with – like the bank, a credit card company, even government bodies – and try to get you to reveal sensitive information, which these days could even just be your voice.

What to do about number spoofing?

Blackstar recommends following OFCOM’s advice:

  • Never give out personal information on an incoming call.
  • Never rely on the Caller ID as the only means of identifying the person on the other end. This is especially important if the caller asks you to do something which could have financial repercussions.
  • Don’t provide any information that is asked of you on an incoming call. Hang up, and search for a contact number for the company and call it to verify the inbound call you received was genuine.
  • Wait at least 5 minutes before making this call, or even better, call from a different phone. This ensures the line has cleared and you’re not still speaking to the fraudster.
  • Report the incident to Action Fraud. Action Fraud is the reporting centre for fraud and cybercrime in England, Wales, and Northern Ireland (In Scotland, report directly to the Police via 101).  They can be reached on 0300 123 2040 or

What if my number has been spoofed?

Unfortunately, number spoofing can work the other way too.  Instead of receiving a call where the number presented to you isn’t genuine, a fraudster could potentially spoof your number to other people.  This could potentially have a negative impact on you, particularly if the fraudsters are aggressive in their tactics.

If your number has been spoofed we recommend you take these actions:

  • Change your number. If you have another number you’re able to present, such as a direct dial, a non-geographic number, or even blocking your number, take this action.  If we manage your SIP trunks or PBX, Blackstar can help you with this.
  • Record a message to let callers know that you’re aware your number has been spoofed. It could say something along the lines of

“If you received a call from (number), please understand that it has been spoofed and is being used without my permission.  Please do not engage with this caller and please block this number.”

The more people who block your number, the less value it has to the scammer.

Again, if Blackstar manages your PBX, we can provide you with assistance here.

  • You should always report your number being spoofed to Action Fraud on the contact details above.

Scammers tend to move through numbers fairly quickly, so you shouldn’t need to rely on the first two bits of advice for more than a couple of weeks.

Unfortunately, the technology which makes it so easy for us all to communicate and do business today is the same technology that is used in spoofing.  The Internet Engineering Task Force (IETF), which helps to develop internet standards, has created a group specifically to tackle spoofing and other forms of telecommunications fraud.  For the time being though, the best defense is word of mouth – if you receive a suspicious communication, or if you think your number has been compromised – tell other people.

If you have any questions please email [email protected] or visit for their official guidance.