Hassell and Macaulay built a proof-of-concept for that spoofing attack using a fake sign-in for the Skype Android app.

FORBES: Researchers Show Android Vulnerable To App-Hijacking Attacks

The UK is already investigating claims that six of those involved in the attack were travelling on fake British passports.

BBC: Urgent question

But the trick could be scaled up to hundreds or thousands of fake signals, much like a denial-of-service attack that uses thousands of computers to choke a website with a flood of fraudulent requests for information, Costin says.

FORBES: Next-Gen Air Traffic Control Vulnerable To Hackers Spoofing Planes Out Of Thin Air

Faheem Ahmed Ansari, an Indian citizen who carried a fake Pakistani passport, sits in an Indian jail awaiting trial on charges of planning a suicide attack on Mumbai's stock market and the Churchgate railway station.

CNN: Two suspected of ties to Mumbai attackers' cell phones