Messages, Dialer apps sent text, call info to Google

Google’s Messages and Dialer apps for Android devices have been collecting and sending data to Google without specific notice and consent, and without offering the opportunity to opt-out, potentially in violation of Europe’s data protection law.

According to a research paper, “What Data Do The Google Dialer and Messages Apps On Android Send to Google?” [PDF], by Trinity College Dublin computer science professor Douglas Leith, Google Messages (for text messaging) and Google Dialer (for phone calls) have been sending data about user communications to the Google Play Services Clearcut logger service and to Google’s Firebase Analytics service.

“The data sent by Google Messages includes a hash of the message text, allowing linking of sender and receiver in a message exchange,” the paper says. “The data sent by Google Dialer includes the call time and duration, again allowing linking of the two handsets engaged in a phone call. Phone numbers are also sent to Google.”

The timing and duration of other user interactions with these apps has also been transmitted to Google. And Google offers no way to opt-out of this data collection.


From the Messages app, Google takes the message content and a timestamp, generates a SHA256 hash, which is the output of an algorithm that maps the human readable content to an alphanumeric digest, and then transmits a portion of the hash, specifically a truncated 128-bit value, to Google’s Clearcut logger and Firebase Analytics.

Hashes are designed to be difficult to reverse, but in the case of short messages, Leith said he believes some of these could be undone to recover some of the message content.

“I’m told by colleagues that yes, in principle this is likely to be possible,” Leith said in an email to The Register today. “The hash includes a hourly timestamp, so it would involve generating hashes for all combinations of timestamps and target messages and comparing these against the observed hash for a match – feasible I think for short messages given modern compute power.”

The Dialer app likewise logs incoming and outgoing calls, along with the time and the call duration.


The paper describes nine recommendations made by Leith and six changes Google has already made or plans to make to address the concerns raised in the paper. The changes Google has agreed to include:

  • Revising the app onboarding flow so that users are notified they’re using a Google app and are presented with a link to Google’s consumer privacy policy.
  • Halting the collection of the sender phone number by the CARRIER_SERVICES log source, of the 5 SIM ICCID, and of a hash of sent/received message text by Google Messages.
  • Halting the logging of call-related events in Firebase Analytics from both Google Dialer and Messages.
  • Shifting more telemetry data collection to use the least long-lived identifier available where possible, rather than linking it to a user’s persistent Android ID.
  • Making it clear when caller ID and spam protection is turned on and how it can be disabled, while also looking at way to use less information or fuzzed information for safety functions.


Leith said there are two larger matters related to Google Play Service, which is installed on almost all Android phones outside of China.

“The first is that the logging data sent by Google Play Services is tagged with the Google Android ID which can often be linked to a person’s real identity – so the data is not anonymous,” he said. “The second is that we know very little about what data is being sent by Google Play Services, and for what purpose(s). This study is the first to cast some light on that, but it’s very much just the tip of the iceberg.”

Source: Messages, Dialer apps sent text, call info to Google • The Register

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