D-Link DFL-600 - Manual (Page 70)

Policy Status page, “Default allow all” means that the DFL-600 will allow
all packets except those that meet the criteria established in the policy rules.
“Default deny all” means that the DFL-600 will deny (filter) all packets
except those that meet the criteria established in the policy rules.
Policies − Policy Add
Once you have defined what type of packets you want the DFL-600 to look
for, you need to assign those rules to a policy. Clicking on the Policies link
will open the Policy Add page, as shown below.