What Data Do The Google Dialer and Messages Apps On Android Send to Google?

We report on measurements of the data sent to Google by the Google Messages and Google Dialer apps on an Android handset. We find that these apps tell Google when message/phone calls are made/received. The data sent by Google Messages includes a hash of the message text, allowing linking of sender and receiver in a message exchange. 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. In addition, the timing and duration of other user interactions with the apps are sent to Google. There is no opt out from this data collection. The data is sent via two channels, (i) the Google Play Services Clearcut logger and (ii) Google/Firebase Analytics. This study is therefore one of the first to cast light on the actual telemetry data sent by Google Play Services, which to date has largely been opaque. We informed Google of our findings and delayed publication for several months to engage with them. On foot of this report Google say that they plan to make multiple changes to their Messages and Dialer apps.