this post was submitted on 19 Dec 2025
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Three billion WhatsApp users are at risk - an expert has developed a tool that could spy on everyone, and you would never know about it

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[–] Nomad 28 points 7 hours ago (3 children)

Security expert here.... This issa nothing Burger and will be fixed on the server side soon I expect. This is about spreading fear uncertainty and doubt. The research is academic in nature and the results are interesting, but this is only a side channel to reveal things like maybe you rough timezone and maybe a few correlations via connectivity quality. This is what they do if they need to confirm if a person uses the same phone number for example. And the could just look it up in the registry or maybe just call you...

This is not a widespread privacy concern, is not very practical to use, especially at scale and is early fixable. Its comparable to the traffic pattern analysis they do to confirm tor users identity if they found them but need supporting evidence. Its what's left when the technology works as intended. So chill your paranoia.

[–] halfdane@lemmy.world 1 points 1 hour ago

While I appreciate your refusal to spread panic, would you mind explaining what the attack does and why it's a nothingburger, maybe even why it's not practical? Because right now, you assert a lot of things without any explanation.

Not saying you're wrong, but I think it's good practice to not just rely on claims of authority

[–] pcouy@lemmy.pierre-couy.fr 1 points 3 hours ago

I believe Signal has already fixed it, while meta said they won't fix this in WhatsApp.

This side channel can be used to infer more than a rough timezone, specifically, an attacker could continuously monitor :

  • the number of devices linked to the target’s account, along with fingerprints that allow differentiation between operating systems and browsers
  • the locked or unlocked state of the target’s phone
  • whether the phone is connected via Wi-Fi or a mobile network
  • whether the WhatsApp application or browser tab is running in the foreground or background.

In addition, an attacker could deliberately drain the target’s phone battery and consume their mobile data allowance

I've tested this on myself and can confirm all of this can be done reliably

[–] hoshikarakitaridia@lemmy.world 7 points 7 hours ago (1 children)

IT hobbyist here. This guy knows his stuff. Dangerous attacks are the ones that are very low effort with medium to high reward. This attack is high effort and low reward. This is one of these trivia things, that you will virtually never see in the wild.

[–] pcouy@lemmy.pierre-couy.fr 0 points 6 hours ago* (last edited 6 hours ago)

This is not high effort. Starting from an open source WhatsApp client library, reproducing the attacks described in the research paper is trivial. There are even a few public github repos implementing PoCs of this.

Whether the reward should be considered high or low is ultimately subjective. What is objectively verifiable, however, is that an attacker can continuously (and silently) monitor several aspects of a target’s environment, including:

  • the number of devices linked to the target’s account, along with fingerprints that allow differentiation between operating systems and browsers
  • the locked or unlocked state of the target’s phone
  • whether the phone is connected via Wi-Fi or a mobile network
  • whether the WhatsApp application or browser tab is running in the foreground or background.

In addition, an attacker could deliberately drain the target’s phone battery and consume their mobile data allowance.