Data Review
-----------

**Everything that lands in mozilla-central that adds or expands data
collection must go through the data review process.**

The data review process is in place to ensure we follow Firefox's
:doc:`standards for data collection <data-collection>`.

This will require assessing the sensitivity of the data that is being
collected, and going through the `sensitive data collection
process <https://wiki.mozilla.org/Data_Collection#Step_3:_Sensitive_Data_Collection_Review_Process>`__
if necessary. All data collection is subject to our `overall data
collection policy <https://wiki.mozilla.org/Data_Collection>`__.

Documentation for the data collection request process and the
expectations we have for people following it `lives on the
wiki <https://wiki.mozilla.org/Data_Collection#Requesting_Data_Collection>`__.
This document describes the technical implementation in Phabricator
using tags.

1. Any change that touches metrics will be automatically flagged with a
   ``needs-data-classification`` tag by Phabricator, using `this herald
   rule <https://phabricator.services.mozilla.com/H436>`__. If a change
   adds/updates data collection in a way that doesn’t automatically
   trigger this rule, this tag should be added manually (and if
   appropriate, please file a bug to update the herald rule so it
   happens automatically next time).

2. After assessing data sensitivity, the tag can be replaced with either
   ``data-classification-low`` or ``data-classification-high`` depending
   on that sensitivity.

3. Adding ``data-classification-high`` will auto-add the ``#data-stewards``
   reviewer group as a blocking reviewer for the change and initiate the
   `sensitive data review process <https://wiki.mozilla.org/Data_Collection#Step_3:_Sensitive_Data_Collection_Review_Process>`__.

4. For patches making mechanical changes that happen to trigger the
   herald rule linked above, but that do not actually add or update any
   data collection, the ``data-classification-unnecessary`` tag can be used.

Patches with the ``needs-data-classification`` tag will not be landable in
Lando. The process linked above must be followed in order to land the
change.
