Beware of telephone spoofing
or how to protect yourself from scammers
With the increasing use of digital technologies, the number of cyber threats that can endanger individuals and organisations is also increasing. One of these threats is phone spoofing – a form of fraud in which an attacker manipulates the caller’s number to impersonate another person or institution. How does this trick work, and how can you defend yourself against it?
What is phone spoofing?
CLIP (Calling Line Identification Presentation) is the caller’s number that is displayed on your phone whenever someone calls you. Phone spoofing is a technique in which a fraudster fakes the CLIP to deceive you as the recipient of the call. They can pretend to be a bank, an office, a company or anyone else. The goal is typically to obtain sensitive information or to induce the victim to take a specific action.
How to protect yourself?
Verify the caller – If you receive a call that seems suspicious, hang up. Ensure it is a number you are calling at a reasonable cost (not a foreign line, not a specially paid line, etc.) and call back (this will contact the actual user of the number).
Never disclose sensitive information – Banks and institutions never ask for passwords or PIN codes over the phone.
Be cautious – If someone is urgently pressuring you to take immediate action (for example, to transfer money), be suspicious and do not let yourself be pressured into making a quick decision.
Czech institutions are also working on protection against spoofing – Czech telecommunications operators are taking active steps to protect their customers from telephone spoofing. T-Mobile and O2 have introduced protective firewalls that detect and block fraudulent calls. In October 2024, these companies implemented a system enabling mutual verification of calls between their networks, thereby increasing the effectiveness of protection. Vodafone joined the same in April 2025.
In addition to the operators’ activities, the Czech Telecommunications Office has implemented regulatory measures that have led to the blocking of millions of fraudulent calls per month and a decrease in fraud.
Conclusion
Telephone spoofing is a serious threat that can lead to financial losses, data breaches, or damage to a company’s reputation. Prevention and consistent control of suspicious calls are the key to protecting against these attacks. Always stay one step ahead and never underestimate the importance of cybersecurity!
The author of the article is Martin Vacek, Head of Communication Technology, PREGIS, a.s.
Published 6 November 2025