Several popular brands of wireless keyboards have been betraying their owners, broadcasting their keystrokes for savvy hackers to intercept from hundreds of feet away.

According to research published Tuesday by Bastille, a cybersecurity company, eight wireless keyboards manufactured by major electronics companies transmit information in a way that makes it possible for a hacker to eavesdrop on every sentence, password, credit card number, and secret typed on them.

Wireless keyboards generally protect their users by encrypting the data they send back to the computers they’re paired with. That way, even if hackers try to listen in on the data stream, they’ll get nothing but an undecipherable mess. Sometimes, however, the encryption isn’t well executed: Last year, a prolific security researcher found a weakness in the encryption used by certain Microsoft keyboards, and built a small device to intercept and decode what’s being typed on them.

That’s the sort of vulnerability that Marc Newlin, a researcher at Bastille, was looking for when he set out to hack 12 popular models of wireless keyboards from brands like Hewlett-Packard, Toshiba, Radio Shack and General Electric. What he found, though, was even more shocking than a poorly secured data connection: Some keyboards weren’t encrypting the keystrokes being tapped out on them at all.

Newlin started out by reverse-engineering the transceivers—the little USB dongles that come with wireless keyboards—to try and determine how they communicate.

“I thought this was going to be just the first part of the process,” Newlin said. “It turned out after completing that step that, lo and behold, all of the keystroke data was simply being transmitted in cleartext, with no encryption whatsoever.”

That oversight makes it easy for a hacker to spy on everything being typed on one of the susceptible keyboards—from as far away as 250 feet. That means an attacker in the next office suite or hotel room could eavesdrop on a keyboard for an extended period of time, without the keyboard’s user ever even realizing it. And if the hacker wanted, he or she could send fake signals to the victim’s computer, tricking it into typing something that was never actually tapped out on the keyboard itself. Bastille dubbed the hacking tool “KeySniffer.”

The hardware Newlin needed to mount the attack is affordable: He used a radio transponder meant for controlling drones, which is available on Amazon for around $40, and a $50 antenna to boost the range to about 250 feet. With that setup, it’s also easy for any attackers to find new keyboards to exploit. As long as a vulnerable USB dongle is plugged into a computer that’s running, Newlin said, it constantly transmits a signal that tips hackers off to its presence.

The keyboards vulnerable to KeySniffer are all low-end, inexpensive models. A list of them is available here—but there could easily be more out there that haven’t been tested yet. Keyboards that connect via Bluetooth, a widely used technology for communicating wirelessly with nearby devices, can’t be hacked with the KeySniffer method, because Bluetooth encrypts data streams in a much more secure way. Wired keyboards are safe, too, because they don’t broadcast a signal at all.

Bastille’s experts say there’s no way to patch the security hole in the affected keyboards. If you’ve got one, the only recourse is to throw it out and replace it with a secure Bluetooth or a wired keyboard.

Tuesday marks the 90th day since Bastille’s researchers informed the keyboard manufacturers about KeySniffer. The three-month lag before publicly releasing the information is designed to allow the companies to fix the problem, in this case likely by recalling the affected hardware. But very little appears to have happened during that time.

“Frankly, we were disappointed with the response we got from the manufacturers,” said Ivan O’Sullivan, Bastille’s chief revenue officer. “Most of the response was no response.”

I reached out to the manufacturers of the eight keyboards found to be vulnerable, and heard back only from three.

The problematic keyboard sold under the General Electric name is in fact manufactured by Jasco, a company licensed to use the GE trademark. In a statement, a spokesperson for Jasco said the company is aware of the issues with its wireless keyboard, and that although it hasn’t been able to replicate the problem, it plans to notify consumers of the problem on its website. The spokesperson said Jasco will “address any customer concerns” if they call into its tech-support line.

A statement from Insignia, Best Buy’s in-house electronics brand, was less conciliatory.

“Insignia Wireless Keyboard & Mouse products incorporate encrypted communication,” a spokesperson said, adding the company will take “immediate action if necessary.” (Newlin said it’s possible some of the company’s products use encryption, but the specific model he tested doesn’t.)

A spokesperson for Anker, a company that makes batteries, chargers and small electronic devices, said Bastille’s email got caught in a spam filter. The company will review the researchers’ claims, the spokesperson said.

O’Sullivan noted Microsoft, which manufactured the wireless keyboards that were hacked earlier, didn’t make the list of keyboards vulnerable to KeySniffer this time.

“Microsoft listened,” he said. “That’s one of the things we’re looking for here.”

Although Bastille is going public with its findings, it’s stopping short of releasing the KeySniffer code into the wild. But that doesn’t mean a similar tool isn’t already out there.

“Marc’s a super smart guy,” O’Sullivan said of the researcher who developed KeySniffer. “But is he the only guy who could have written this? No. Is it out there? We don’t know. When there’s been one smart guy doing it, who knows who else has already done this?”