Rule Set 2: The firewall device is never accessible directly from the public network. If attackers
can directly access the firewall, they may be able to modify or delete rules and allow
unwanted traffic through. For the same reason, the firewall itself should never be allowed
to access other network devices directly. If hackers compromise the firewall and then use its
permissions to access other servers or clients, they may cause additional damage or mischief.
The rules shown in Table 6-7 prohibit anyone from directly accessing the firewall, and prohibit
the firewall from directly accessing any other devices. Note that this example is for the
external filtering router/firewall only. Similar rules should be crafted for the internal router.
Why are there separate rules for each IP address? The 10.10.10.1 address regulates external
access to and by the firewall, while the 10.10.10.2 address regulates internal access. Not all
attackers are outside the firewall!
Note that if the firewall administrator needs direct access to the firewall, from inside or outside
the network, a permission rule allowing access from his or her IP address should preface
this rule. Be aware that it is possible to access the interface on the opposite side of the
device, as traffic would be routed through the box and “boomerang” back when it hits the