Are you on your iPhone? And can you see an alluring public Wi-Fi network with loads of percentage symbols in the title? DON’T JOIN IT, PAL! OH GOD NO.
Why? Well, Carl Schou — a security researcher based in Denmark — has unearthed a zero day that can scramble the Wi-Fi on iPhones or other iOS devices. Here’s what he posted:
According to Schou, joining this network knocked out his iPhone‘s Wi-Fi. He tried resetting network settings and force restarting the device, but nothing worked until he manually edited the iPhone backup .
This experience may not be universal though. When this was shared on Reddit, some users on the site joined a network with this name without any difficulties.
What’s worrying is that this issue with the percentage symbol in Wi-Fi networks names isn’t new. Schou himself reported a similar issue a few weeks back where joining a network called “%p%s%s%s%s%n” on the iPhone disabled Wi-Fi:
The reason percentage symbols are causing an issue with the iPhone‘s Wi-Fi is down to the C computer programming language. The “%” symbol is a C string format specifier. It’s likely that the name of the network is triggering a string format process on the iPhone and that’s crashing the Wi-Fi functionality.
If you’d like more technical detail, this piece on The Register breaks down what likely happened with the “%p%s%s%s%s%n” network mentioned above. We can assume something similar’s going on with the “%secretclub%power” name.
I will say it’s surprising that Apple hasn’t done anything to fix this yet. Even though this issue doesn’t seem dangerous, it is embarrassing.
So here’s the question: What can you, an iPhone user, do to avoid having your Wi-Fi tanked by a mysterious network?
Well, it’s quite simple: don’t join any random ass public networks. And be especially wary of any that have percentage symbols in their name.
