Using GAT+ Alert rules, an Admin can get notified if Google Drive document when shared outside your domain contains email addresses. This is one example of using the regex feature inside of Alert Rules.
To set up an alert
Open GAT+ and navigate to Alert rules
Click on the + sign, pick and add a name for the rule.
Select and enable the rule.
In Type select Drive pick and select the Scope of the users you want to check for.
Place recipients who will be notified once the rule is broken and a file is shared out containing text based on the regex rule.
Under Alert, if regex matches a newly shared out file (Google types only) click on the + sign and add the regex
For the Pattern ( in the regex we have searched for email addresses contained in the Shared out document)
The regex example:
This contains ( @gmail.com @yahoo.com and @outlook.com ) – as a regex example.
Additionally, select Notify user if you would want to send a message to the user or Remove shares if you want to directly remove the sharing permissions of this document.
Select to Save the rule.
The rule will be saved and later can be viewed, edited or removed from the options under Actions.
When a google document is shared out and if it contains an email address (based on the regex) in its content an alert will be triggered.