Alexis Lours, a software engineer and technical writer from France, has published a detailed analysis of the new Lockdown Mode added to iOS 16 in the third beta.
There is good news and bad news. It protects your iPhone from some of the most advanced cyber attacks in the world (like Pegasus). But it will also greatly slow down the performance while browsing the web.
What is iOS 16 Lockdown Mode?
Before we get into Lours’ tests, it’s worth explaining what Lockdown Mode is and what it’s for. This is not, we want to emphasize, a feature intended for the average user. It’s an ultra-high privacy mode for individuals who fear cyber-attacks “from private companies that develop state-sponsored spyware for mercenaries.” Here’s Apple’s explanation:
“Lockdown mode is an extreme, optional protection that should only be used if you believe you could be the personal target of a highly sophisticated cyber-attack. Most people are never the target of attacks of this nature.”
(Read Apple’s press release for a slightly more detailed guide to the purpose of Lockdown Mode.)
In other words, you probably won’t use this mode unless you’re a Saudi monarchist journalist or a Russian ex-pat looking for oligarchs. However, it’s still interesting to look at how it works, which can provide insight into Apple’s approach to privacy and the performance costs of extreme privacy protections.
What Does Lockdown Mode Do?
“When the iPhone is in lock mode,” explains Apple, “it won’t work as usual. Apps, websites, and features will be strictly restricted for security, and some experiences will be completely unavailable.”
This is important. Lockdown mode doesn’t wield a magic wand and magically protects an iPhone from cyber-attacks; rather, it’s a compromise that disables many of the iPhone’s features to make attacking the device more difficult.
After testing, Lours offers this list of features that are disabled, in most cases “as a way to reduce potential user tracking”.
- MP3 Playback
- Gamepad API
- Web Audio API
- JPEG 2000
- Speech Recognition API
- PDF viewer
- SVG Fonts
A non-engineer will likely find much of that list baffling. What actual differences will they notice in real iPhone usage?
How Much Will Lockdown Mode Slow Down My iPhone?
- Speedometer 2.0, which measures “web application responsiveness”
- MotionMark 1.2, which measures “a browser’s ability to animate complex scenes at a target frame rate”
Using Lockdown mode resulted in 95%, 65% and 20% performance drops in the three respective tests. That’s quite a variation, but suggests that the mode should only be used by the most at-risk users.
iOS 16 is currently in beta testing and could change significantly before it launches in the fall. We’ll wait with interest to see if Apple can find a way to mitigate this performance drop, but it’s likely that extreme protections simply require extreme compromises.