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Even after deleting the app, FBI copies Signal messages from iPhone

The FBI has been investigating over a dozen individuals in connection with an incident at the Prairieland Immigration and Customs Enforcement detention center in Texas last summer. As part of the probe, investigators sought the group’s Signal messages.

According to 404 Media, the FBI was able to make forensic copies of messages that appeared on a defendant’s lock screen, even though the app had been deleted. It turns out that iPhones store push notifications in a database on the device. A website dedicated to support for the defendants shows how the content of the messages (Exhibit 158) on one individual’s phone was used as evidence in the case.

What you can do

  • Tighten Signal’s notification settings. Using the app’s settings, we always recommend preventing the content of your Signal messages from appearing on your screen. This will prevent “shoulder surfers” from reading your messages, as well as anyone who simply picks up your phone. The Prairieland case is just one more reason to prevent content from appearing in your notifications. Read our guide to locking down Signal.
  • This is not just about Signal. The underlying issue is that the iPhone caches items that appear as notifications on your lock screen. This could apply to all apps with notifications. We hope that Apple will severely limit the time that messages are cached to minimize risk to users. But in the meantime, if this is a problem for you, you can disable notifications for other sensitive apps. Go into your Settings and tap on “Notifications.” From here, you can choose any app that should have notifications disabled.

Updates from our team

  • My colleague Caitlin Vogus and I examined how the U.S. intelligence community may spy on Americans who use VPNs, and the need to reform foreign intelligence surveillance law. Give it a read!
  • My digital security teammate, Davis Erin Anderson, will be at the JEA/NSPA National High School Journalism Convention from April 16-18 in Minneapolis. If you’re around, be sure to say hi — we often have digital security digest stickers on hand.

Our team is always ready to assist journalists with digital security concerns. Reach out here, and stay safe and secure out there.

Best,
Martin

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Martin Shelton
Deputy Director of Digital Security
Freedom of the Press Foundation