Why does it seem so hard to keep government information classified? Donald Trump and Joe Biden both took top-secret documents to their houses. Hillary Clinton kept State Department emails on a personal server. This week, the White House added a journalist to a group chat about bombing Yemen.

The administration argues it wasn’t a big deal. But security experts say the Signal thread, in which The Atlantic’s editor was accidentally included, was a sloppy and dangerous mistake.

There are several reasons this sort of lapse keeps happening — and the Trump administration is uniquely prone. Today’s newsletter will break them down and explain the stakes.

There are computer systems designed to discuss war plans and other secrets. They are accessible only in secured rooms, and it’s very difficult for foreign powers to penetrate them. You can’t bring your personal devices into these rooms, which are not connected to the web.

But all that security makes them cumbersome and annoying. In most secured rooms, you can’t toggle between work and social media, the way most of us do. You can’t scroll through a classified feed while watching “The White Lotus.” For all but the top officials, who have Sensitive Compartmented Information Facilities, or SCIFs, built at their homes, you have to go into the office to check on “the high side,” the slang for the secret computer networks.

Government officials, including new political appointees like the ones in the Signal chat, are trained on the proper protocols, and it can be a crime to violate them. But it’s hard to toggle between an economic speech in Michigan, which the vice president was giving on the day he weighed in, and the monkish habits needed to interact with restricted material. Biden administration officials sometimes used Signal, too, though more for directing colleagues to SCIFs for updates than for sharing the government secrets that could be found there.

Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.

Thank you for your patience while we verify access.

Already a subscriber? Log in.

Want all of The Times? Subscribe.