iPhones can be broken by just watching one short video

The bug is being used as a prank — but could have far more worrying applications

An iPhone that caught fire. In this case the breaking is far less spectacular and entirely temporary

One apparently innocuous video can break your phone.

The new video is exploiting a bug that can lead to phone’s gradually slowing down until they crash. The trick – being sold as a prank – is next to impossible to avoid and people who are experiencing it might not even be aware of the fact.

The video only lasts three seconds and is being shared on an app called Miaopai. But people might not know that before being subject to the attack, because all that needs to happen is someone clicks on an otherwise innocuous-looking link.

Even the video itself would look fine. But once it is over then the video will slowly force the phone to break – and up to a minute later the phone will ground to a complete halt and need to be turned off.

That needs to be done through a force restart. On the iPhone 7 that’s done by holding the volume down and lock button, and on phones with a normal home button it’s triggered by pressing that button as well as the one on the side.

If the device is restarted then the phone appears to return to normal, though it could easily be still affected by problems that don’t make themselves so obvious.

The trick appears to use a buffer overflow trick to break the phones. That happens when the phone is trying to get hold of more data than it can actually store, leading the phone to stop working properly.

That can be worrying not only because it is annoying to have a phone turn off. Buffer overflows can also be an easy way of forcing phones or other devices to load up bad code – which might then allow people to monitor what’s happening on a phone or steal data, for instance.

In that way, it is similar to the “effective power” bug that led phones to break down if they just received one message. That was mostly used as a prank – sending the text to friends – but it was a way of using a hack that could easily be exploited for far more dangerous and malicious ends.