Yesterday I received a group text message from a number I don't know and opened it by mistake. I was in a group chat with two other people, one in Pennsylvania one in Massachusetts. The message body was the phrase "knows what" and attached was a file called voicenote.amr. The file was a 5 or so second clip of what sounded like paper rustling.

My question is what is the point of a spam text like that and what information could I have disclosed by accidentally opening it? I've gotten spam texts in the past but they are usually some sort of phishing.

EDIT: I am running Andriod version 4.4.4 and using the default texting app called "Messaging" it is also version 4.4.4. It handles both group and regular texts.

  • Hi, can you edit your question to include what operating system your phone is running (Android version X, iOS version X, etc), which SMS client you're using, and which group chat program you're using? Dec 1 '15 at 21:03
  • Updated, let me know if there's anything I left out.thanks for the response!
    – mercurial
    Dec 1 '15 at 21:12
  • Possibly stagefright exploit?
    – Daniel Ruf
    Dec 1 '15 at 21:17

My guess is that the sender is trying to exploit the recent StageFright vulnerability, but since you have the latest Android security patches, you just got a dumb audio file.

If the attack had been successful, it would have gained root access to your phone and removed all traces of the original sms.


There is a strong possibility this is a Stagefright virus. It exploits a flaw in the default audio player to infect the device. Fortunately for you patches were released for version 4.4.4. I would still scan your device for any affects left by this and would avoid opening files sent from unknown sources in the future.

  • First time I've heard of it being used in the wild.
    – Dylan Katz
    Dec 3 '15 at 1:35
  • Stagefright exploit attempts are very common in the wild since it targets a wide range of devices.
    – Bacon Brad
    Dec 3 '15 at 2:02

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