Security experts have warned of a new vulnerability which could leave the iPhone and other mobile phones open to attack.

Researchers Charlie Miller and Colin Mulliner revealed the flaw during a presentation at the Black Hat USA 2009 conference in Las Vegas. The vulnerability was demonstrated on iPhone, Android and Windows Mobile smartphones and, according to reports, can be prevented only by turning the handset off.

If exploited, the vulnerability could allow an attacker to take control of a handset and use the device to send spam or install malware.

Vulnerabilities and attacks for mobile phones have become a fast-growing branch of the malware business in recent years. As vendors have developed new security tools and protections for increasingly complex devices, malware writers have sought new ways to capitalise on the growing sector.

Some of the most recent developments have included a mobile botnet, which prompted researchers to warn that the mobile malware industry could be ready to make significant growth in the coming years.

Discovering flaws in Apple products is nothing new for Miller. The researcher has won the last two Pwn to Own contests run at the CanSecWest security conference. Miller's most recent triumph involved taking control of a fully-patched MacOS X system running Safari in under two minutes.