CEO Steve Jobs said Apple is upping attempts to prevent hackers unlocking the iPhone handset.

Jobs statement at yesterday's UK iPhone launch marks the first time Apple has officially said it would fight attempts to use the popular device on unauthorised networks.

At a London Apple retail store where he announced the iPhone's November 9 release and confirmed O2 had the exclusive deal to offer the iPhone in the UK, Jobs responded to a question about whether Apple would put a stop to the unlocking hacks that have mushroomed recently. "It's a cat-and-mouse game," said Jobs. "We try to stay ahead. People will try to break in, and it's our job to stop them breaking in."

(See also: The hidden costs of UK iPhone hacks)

In last few weeks, people have unveiled several unlock hacks that let users swap the iPhone's included SIM card with one from another cellular service provider so the phone can make calls on that carrier's network. With the iPhone limited to domestic sales until November, unlocking is the only way consumers living outside the US have been able to use their phones.

Last week, the iPhone Dev Team posted a free unlocking hack (see Free Apple iPhone unlock hack released), then followed it Monday with anySIM, an unlocking tool tucked into a graphical interface. Just a day before the iPhone Dev Team released its free hack, a group called iPhoneSIMFree began selling an unlocking tool of its own through a network of online resellers at prices ranging from $45 to $99.

Jobs did not go into details on how Apple would bar hacks, but the process would presumably involve firmware updates to the iPhone, delivered via the iTunes software. Both of the firmware updates issued since the iPhone's US debut in late June have either broken other, non-unlocking hacks, or forced users to restore the device from scratch. IPhoneSIMFree, for instance, does not guarantee that its unlocking tool will work after future firmware updates.

Keeping unlocking hacks completely at bay, though, will probably be impossible, something Jobs tacitly acknowledged when he said that while it was a cat-and-mouse game between Apple and hackers, "I'm not sure if we are the cat or the mouse."

"Jobs said that they would stay a step ahead," said Milanesi, "but that will be easier said than done."

Jonny Evans and Karen Haslam of MacWorld UK contributed to this story.

See also:

How to unlock an Apple iPhone for free

O2's UK iPhone sacrifices revealed

Top 25 requests for the UK Apple iPhone

Apple iPhone: the definitive review

The 10 most ridiculous iPhone stories so far

Apple working on iPhone version 2