A Signal update fends off a phishing technique used in Russian espionage

Russia-linked groups [...] are taking advantage of a Signal feature that allows users to join a Signal group by scanning a QR code from their phone. By sending phishing messages to victims, often over Signal itself, both hacker groups have spoofed those group invites in the form of QR codes that instead hide javascript commands that link the victim's phone to a new device—in this case, one in the hands of an eavesdropper who can then read every message the target sends or receives.

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Two months ago, Google began warning the Signal Foundation that maintains the private communications platform about Russia's use of the QR code phishing technique, and Signal last week finished rolling out an update for iOS and Android designed to counter the trick. The new safeguard warns users when they link a new device and checks with them again at a randomized interval a few hours after that device is added to confirm that they still want to share all messages with it. Signal now also requires a form of authentication such as entering a passcode or using FaceID or TouchID on iOS to add a new linked device.

In fact, Signal had already been working to update those forms of phishing protections aimed specifically at exploitation of its linked device feature prior to Google's warning, says Signal's senior technologist, Josh Lund. But Google's report about Russia's spying in Ukraine provided an “acute” example of the problem that pushed them to move quickly to protect users, he says.

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Both Google and Signal emphasized that the phishing technique Google has seen in use in Ukraine doesn't suggest that Signal's encryption is broken or that the app's messages can otherwise be eavesdropped in transit. Instead, the trick essentially combines two legitimate features—QR-code group invites and QR-code device linking that pairs a smartphone with a laptop—invisibly swapping one with the other to deceive users.

Mirror: https://archive.is/MbR9e

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