Two weeks after exposing a screenshot privacy issue in iPhone, hacker Jonathan Zdziarski has figured out a way to prevent it.
Zdziarski explained to Wired.com that the issue occurs when you press the Home button on the iPhone to return to the main screen, and the window of the application you have open shrinks and disappears. In order to produce that shrinking effect, the iPhone snaps a screenshot and temporarily stores it -- and hackers or forensics experts can eventually recover these photos. To fix the problem, you'd essentially have to disable the handset from storing the screenshots, he told Wired.com in an e-mail.
Granted, fixing the problem requires hacking -- or "Jailbreaking," as the community calls it -- your iPhone yourself. (Steps on that procedure can be found at the iPhone DevTeam blog.) And as you might imagine, tampering with that effect will make things less pretty: When resuming an application, you'll get the default screen, since you'll no longer have stored screenshots cached. For example, when re-launching your Mail application it will always zoom to the front and appear as though it's empty, but after the application fully resumes it'll look normal, Zdziarski explained.
Nonetheless, if privacy is your utmost concern, here are the steps:
1. After Jailbreaking your iPhone, use an OpenSSH application to gain root privileges to your iPhone.
2. Using the OpenSSH app, enter the following commands in the prompt:
- # rm -rf /var/mobile/Library/Caches/Snapshots
- # ln -s /dev/null /var/mobile/Library/Caches/
Snapshots
Those commands will disable screenshot writing. And if you wish to undo this, delete the symlink and the directory will get recreated.
This sort of tampering isn't for the faint of heart, so exercise caution. And though this workaround addresses one major privacy issue, Zdriarski stresses that there are still plenty of other ways forensics examiners and hackers can recover other data, such as your keyboard cache, Safari cache and Google Maps lookups.
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