Careless Whisper: Exploiting Silent Delivery Receipts to Monitor Users on Mobile Instant Messengers
arxiv.org
With over 3 billion users globally, mobile instant messaging apps have become indispensable for both personal and professional communication. Besides plain messaging, many services implement additional features such as delivery and read receipts informing a user when a message has successfully reached its target. This paper highlights that delivery receipts can pose significant privacy risks to users. We use specifically crafted messages that trigger delivery receipts allowing any user to be pinged without their knowledge or consent. By using this technique at high frequency, we demonstrate how an attacker could extract private information such as the online and activity status of a victim, e.g., screen on/off. Moreover, we can infer the number of currently active user devices and their operating system, as well as launch resource exhaustion attacks, such as draining a user's battery or data allowance, all without generating any notification on the target side. Due to the widespread adoption of vulnerable messengers (WhatsApp and Signal) and the fact that any user can be targeted simply by knowing their phone number, we argue for a design change to address this issue.
  • Screen_Shatter@lemmy.world
    73·
    20 hours ago

    I remember trying to sign up for signal and stopped when it wanted my phone number. It’s no longer anonymous at that point. When I talk about it theres always people who come at me about it being secure and whats my attack vector? Well, its not secure. My vector is a desire to be anonymous, and clearly the anonymity this presents is a facade.

    • Arthur Besse@lemmy.mlOPEnglish
      13·
      1 day ago

      You can literally turn off read receipts in signal

      But you can’t turn off delivery receipts, which is what this attack uses.

      • ryannathans@aussie.zone
        11·
        1 day ago

        But you can turn off sealed sender messages from anyone, so they’d have to already be a trusted contact

        • Arthur Besse@lemmy.mlOPEnglish
          12·
          1 day ago

          But you can turn off sealed sender messages from anyone, so they’d have to already be a trusted contact

          The setting to mitigate this attack (so that only people who know your username can do it, instead of anybody who knows your number) is called Who Can Find Me By Number. According to the docs, setting it to nobody requires also setting Who Can See My Number to nobody. Those two settings are both entirely unrelated to Signal’s “sealed sender” thing, which incidentally is itself cryptography theater, btw.

  • Law Abiding VPN User@feddit.orgEnglish
    113·
    2 days ago

    You can’t avoid being monitored on whatsapp, on signal however, just be careful about what you download and be sure to have a good antivirus running and up to date on your devices