ZyXEL Communications ZyWALL USG Series Application Note page 182

Click Configuration > AppPatrol > Query, and in the second dropdown menu, select Instant
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Messager, and click Search. Then, double-click the msn entry to edit it.
Double-click the Default policy .
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Change the access to Drop because you do not want anyone except the authorized user group
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(sales) to use MSN. Click OK.
Now you will need to set up a recurring schedule object first. Click Configuration > Object >
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Schedule. Click the Add icon for recurring schedules.
Give the schedule a descriptive name such as WorkHours. Set up the days (Monday through
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Friday) and the times (08:00 - 17:30) when the sales group is allowed to use MSN. Click OK.