How to Make Your Disappearing Alarm Messages Really Disappear
When it comes to messaging apps, Signal is one of the safest options out there, but it turns out that the service does have a pretty big vulnerability if you’re using it on a Mac.
Your disappearing messages (you know, the ones that should self-destruct after a certain amount of time) are actually stored on your Mac by default. Here’s what you need to know to ensure that any sensitive information sent through Signal actually disappears as intended.
What is the problem?
It all comes down to Notification Center on Mac. If you are using Signal on your computer, each new message will arrive as an alert, which is stored in the Notification Center, where both the content and the sender’s name are clearly visible.
Somewhat surprisingly, this is true even if the messages you receive are supposed to self-destruct. Even after they disappear from the Signal app, they will still be visible in the Action Center and elsewhere on your computer. The problem was originally discovered by security researcher Alec Muffett, who shared his findings on Twitter . After Motherboard noticed the tweet, Patrick Wardle (another Mac security researcher) delved deeper into the Signal security issue.
Lifehacker also reached out to Signal for comment and will update this story if we get a response.
In his blog post, Wardle explains that hackers still need access to your computer (remotely or physically) in order to see your Signal messages. So this is not a problem for most people, but if you actually use Signal to exchange sensitive or valuable information, it can be a real problem. Fortunately, there is an easy way to fix this.
Solution
To make sure the disappearing Signal messages do disappear, simply open the app on your Mac and go to Preferences (click Signal in the upper right corner of your screen and this option should appear). In the “Notifications” section, select “Neither name nor message.” You can also select Sender Name Only if you still need useful information without revealing everything.
The next time you receive a Signal notification on your Mac, it will not save any sensitive information on your computer. Unfortunately, this does not solve the problem of “disappearing” messages already recorded by your Mac, and this is where things get complicated.
Checking your database
With a little coding, Wardle discovered that all of these self-destructing Signal messages were also stored in a database deep inside your Mac. In fact, accessing this information is probably beyond the skills of most people (myself included), but if you’re up for the challenge, you can follow along with Wardle (a professional Mac security researcher) right here.
To make things easier, he also installed a script that can scan your Mac and show all hidden notification data. This way, you will know that there is data to delete before starting the difficult job of cleaning up the database. However, for most of us, just making sure any disappearing messages you receive in the future actually disappear should be more than enough to calm you down.