Donald Trump is still tweeting from his Android phone, despite the best efforts of his aides and national security staff. The New York Times reported on Trump’s unwillingness to give up the phone in January, and in the weeks since, Trump has issued tweet after tweet tagged as “Twitter for Android.” In one picture from 2015, the phone appears to be a Samsung Galaxy S3, an old model that hasn’t received a software update in over a year.

Holding on to a consumer-grade phone is a very dangerous habit for a US president. Foreign intelligence agencies run some of the best and most dedicated hacking teams in the world. For those groups, breaking into a GS3 would be child’s play, which is exactly why the president is usually restricted to a secure phone with limited functionality. Once those hacking groups are inside, they can turn the phone into a live microphone, letting them listen in on any conversations within earshot. That might sound extreme, but it’s an old trick for most digital spying groups — so plausible that some experts believe Trump’s phone may have already been compromised.

To be clear, this isn’t an Android problem. Android phones have more known vulnerabilities — particularly the old version of Android that’s running on the GS3 — but even a perfectly up-to-date iPhone isn’t safe from spyware. A human rights activist in the UAE found that out the hard way this summer, when his phone was targeted with spyware that exploited undisclosed vulnerabilities in iOS. Those vulnerabilities are rare and expensive — but if your target is the president of the United States, there would be no hesitation about using one.

We still don’t know exactly how Trump is using the phone. It might be held by an aide or kept in a desk drawer at home, rather than kept on his person. But while those practices would make the phone a less attractive target, it would still be an easy way to listen in on the president, and an ongoing nightmare for his national security staff. The fix is simple enough — give up the phone — but so far, it seems to be a step Trump simply isn’t willing to take.