Siri security hole could let thieves use your iPhone 4S

Security experts are warning iPhone 4S users of an unintended feature which could allow strangers to use certain functions on their handset, even if it has been locked.

As we found out in the V3 office, the new voice-activated personal assistant feature, Siri, can be a boon to the time-starved iPhone user.

However, Apple has allowed the tool to be used even when the phone has been locked, simply by pressing the home button. Effectively this means a complete stranger could give Siri verbal commands to compose emails, texts, change calendar settings and more.

Although the range of tasks that a would-be thief could carry out on a locked phone via Siri is limited, the fact that it is enabled by default has angered some security experts.

"What's disappointing to me though is that Apple had a clear choice here," wrote Sophos senior technology consultant, Graham Cluley.

"They could have chosen to implement Siri securely, but instead they decided to default to a mode which is more about impressing your buddies than securing your calendar and email system."

To turn Siri off when the phone is locked, users need to go to Settings/General/Passcode Lock and then turn the Siri option to off.