Apple has admitted that it has the ability to remotely disable potentially malicious iPhone and iPod Touch applications that have been downloaded from the App Store.

CEO Steve Jobs confirmed the existence of the 'kill-switch' following a story in the Wall Street Journal earlier this week. Jobs said the 'kill switch' is a last-ditch option if a malicious application slipped through Apple's checks and made it onto the App Store.

"Hopefully we never have to pull that lever, but we would be irresponsible not to have a lever like that to pull," Jobs told the newspaper.

Discussions regarding the switch started last week when Jonathan Zdziarski, a security researcher and author of a pair of books about iPhone development, said he had found a line in the phone's operating system that pointed to a URL. The link, said Zdziarski, led to a page that appeared to be an embryonic blacklist.

The URL, which points to an Apple server, currently contains only placeholder data. Later, Zdziarski updated his site with more information.

"With a little DNS spoofing, I fed my own list into the iPhone and effectively killed (by name) applications that attempt to use the GPS. It looks like that's all it's set to do right now, but I may just not have found the 'vaporise' switch," he said.

Are you considering signing up for one of the bargain mobile broadband contracts currently on offer? See our new price comparison site to make sure you get the best deal

"Either it is an anti-malware solution, and [the iPhone] has a switch somewhere to vaporise any app, or it's not an anti-malware solution and is really designed to kill applications that interfere with Apple's business model, such as unsanctioned traffic navigation software," he added.

Zdziarski then speculated that the URL he'd uncovered might only feed the actual 'kill switch', hidden elsewhere in the OS.

"Unless, for some reason, they decided to build two separate mechanisms into the iPhone to do this, of which the other one is invisible, this one likely feeds a 'master' kill switch. Perhaps there is a special setting in the configuration file which can vaporise the app all together," he said.

"It speaks poorly to the device," argued Andrew Storms, director of security operations at nCircle Network Security. "You should never have been in that situation to begin with, and again brings up the question, 'Is the iPhone really an enterprise device?"

A kill switch should be included in the iPhone's administrative tools, not set by Apple through a URL, Storms said. IT staff can, for instance, remotely disable applications on a company-managed Research In Motion BlackBerry.

"But from a consumer perspective, this is probably welcome," added Storms, though he wondered, as have many others, why Apple shouldn't be expected to sniff out malicious intent before it grants approval to an application and adds it to the App Store.

"On the other hand, how did the 'I Am Rich' app get through?" Storms asked, referring to an application that appeared briefly on the App Store last week before Apple yanked the $999 (£500) program. I Am Rich, which was reportedly purchased by a handful of users, had no function other than to display a ruby-like icon on the home screen of the iPhone.