A United Nations group that advises nations on cybersecurity plans to send out an alert about significant vulnerabilities in mobile phone technology that could potentially enable hackers to remotely attack at least half-a-billion phones.

The bug, discovered by a German firm, allows hackers to remotely gain control of and also clone certain mobile SIM cards.

Hackers could use compromised SIMs to commit financial crimes or engage in electronic espionage, according to Berlin's Security Research Labs, which will describe the vulnerabilities at the Black Hat hacking conference that opens in Las Vegas on July 31.

The UN's Geneva-based International Telecommunications Union, which has reviewed the research, called it "hugely significant".

"These findings show us where we could be heading in terms of cybersecurity risks," ITU secretary-general Hamadoun Touré said.

He said the agency would notify telecommunications regulators and other government agencies in nearly
200 countries about the potential threat and also reach out to hundreds of mobile companies, academics and other industry experts.

A spokeswoman for the GSMA said it also reviewed the research.

"We have been able to consider the implications and provide guidance to those network operators and SIM vendors that may be impacted," said the GSMA spokeswoman.