Siri Passcode Lock
Go to settings -> Security then press the Siri toggle to disable this feature.

Apple's much-touted iPhone 4S feature, Siri, can let others access your e-mail and texts without having to first hack your password.

The hugely marketed voice assistant has been shown to be able to send texts and e-mails even when the phone is locked, meaning anyone could send messages to your contacts.

The Siri-hacking came to light after a PCWorld editor accessed a Macworld employee's texts and e-mails via the voice-activated system despite a password lock. The editor sent a mock resignation e-mail to demonstrate the flaw; fortunately he didn't send it to his boss.

"Siri isn't tuned to a single voice, which means that Siri can be used by someone other than you to send an e-mail or text from your phone," MacWorld said.

The prevention, although easy, isn't what everyday users would expect to need.

Under the password lock screen, users can opt to not let Siri be used whilst the lock is in place. In which case, if the home button is held down, Siri will not activate until the password is entered.

MacWorld continued: "No fake resignation letters are sent to your boss, no demands for a divorce are texted to your spouse."

Siri was been heavily marketed by Apple, but some are hugely disappointed with it.

One person, called TJ670, commented on Apple's Web site: "So far it's been a dismal experience. I've tried everything. It times out easily, has network issues and can't tell the difference between 'David' and 'Thomas' when both have the same last names. I'm not sure what I'm doing wrong."