Julian Oliver is a playful and media-savvy security researcher; previously, he documented hidden cell-phone towers in bad disguises and produced a hand-grenade shaped "transparency device" that spied on everything going on in the room.

Now, Oliver has released a cellular base-station disguised as a boring HP office printer; it is perfectly camouflaged to be set up and plugged in at any office, and then it overpowers the cellular connections from real outside cellular towers, grabs all the phones in the building, and sends them texts that tempt the recipient into conversation ("Come over when you're ready…I'm printing the details for you now") — if the recipients respond, anything they text back is printed on the "HP" printer.

It's a demonstration of how insecure and terrible the GSM standard for mobile connections is. The vulnerability that Oliver exploits to hijack his audience-victims' phones is the same one that cops use with Stingray mass-surveillance devices, which have been secretly used to continuously capture the movements, social relationships and communications of entire populations in countries all over the world.

Oliver's printer also makes random calls to people whose phones it has captured and plays samples from "I Just Called to Say I Love You" to anyone who answers.

He plans to exhibit his printer in a gallery, but only after extensive discussions with lawyers skilled in communications law.

Oliver's creation isn't intended merely to stage an elaborate office prank. He wants to demonstrate the inherent privacy flaws of the cellular connections our phones depend on. His Stealth Cell Tower, after all, is no different from the devices known as IMSI catchers, or "stingrays," that police use to hijack cellphone connections and spy on and track criminal suspects. "GSM is so broken and phones are so desperate to get hooked up that they'll just hop onto anything that looks like a cell tower," Oliver says. "IMSI catchers are most commonly deployed at protests. It's worrying, when you're looking at activist movements organizing themselves over SMS and calls." Instead, he says, his mischievous printer should serve as a reminder to the paranoid to end-to-end encrypt their communications. He recommends the free encryption app Signal. "My project is intentionally built to humiliate GSM in a sense," says Oliver. "It's broken, and we need to encrypt our stuff end-to-end."

Stealth Cell Tower [Julian Oliver]

This Evil Office Printer Hijacks Your Cellphone Connection [Andy Greenberg/Wired]