Starting in Untangle NGFW v.11.2, our Reports module can generate data on Admin logins as well as any changes that have been made to the Untangle server. NOTE: All screenshots are from Untangle NGFW v.13.1
Use the Reports Viewer - this is the "Reports" button that appears at the top of your server's GUI once you've installed the Reports module. Clicking on the button will bring up the Reports Viewer, with various sections and applications to navigate through on the left. For this particular report/event, click the "Administration" option on the left, like in the screenshot below:
From there, click on Administration and you will see both Reports and Events for Admin Logins and Settings Changes:
The reports/events will look similar to these:
By default this report will show you the last 24 hours of activity but, if needed, you can adjust the date range on this report. If you click on the date option it will present you with a clickable calendar. You can select a previous date and then click 'Done' and then 'Refresh':
Keep in mind, how far back you can go will be dependent on the data retention settings in the Reports app. That setting is found under the settings of the Reports service and found on the 'Data' tab. The entry will show as 'Data Retention days'.