Firewall ManagementInterface
Modern firewalls come with two administrative interfaces:
• The CLI
• The GUI (typically, but not necessarily, web based)
This section provides an overview and some examples of these interfaces.
Managing Firewalls with a CLI
A CLI enables you to use a specific instruction set to configure the firewall. Most
firewalls require the end user to do the initial configuration of the firewall (inputting in
the basic network information such as IP address, net mask, default gateway, and
possibly an administrative password) via CLI before the end user can switch over to the
GUI. Linux's NetFilter is, for the most part, configured through a CLI, although there do
exist several products that allow for configuration of NetFilter-based firewalls through a
GUI.
CLIs require knowledge of the command set in the firewall product. For example, to
configure NetFilter, use the IPTables CLI to allow inbound Secure Shell (SSH), e-mail,
and web traffic (using TCP ports 22, 25, and 80, respectively) and deny all other traffic
requires the configuration in Example 11-1
.
Example 11-1. Configuring NetFilter with IPTables
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# iptables -P INPUT DENY
# iptables -P OUTPUT ACCEPT
# iptables -P FORWARD ACCEPT
# iptables -A INPUT -i lo -j ACCEPT
# iptables -A INPUT -p tcp -s 0.0.0.0/0 -d 10.16.17.202 dport 22 -m state
state NEW -
j ACCEPT
# iptables -A INPUT -p tcp -s 0.0.0.0/0 -d 10.16.17.202 dport 25 -m state
state NEW -j
ACCEPT
# iptables -A INPUT -p tcp -s 0.0.0.0/0 -d 10.16.17.202 dport 80 -m state
state NEW -j
ACCEPT
# iptables -A INPUT -m state state ESTABLISHED,RELATED -j ACCEPT
# iptables -A INPUT reject-with icmp-host-prohibited -j REJECT
Example 11-2 provides a similar configuration with the PIX command set.
Example 11-2. Configuring a PIX
gandalf(config)# access-list acl_test permit tcp any host 10.16.17.202 eq ssh
gandalf(config)# access-list acl_test permit tcp any host 10.16.17.202 eq smtp
gandalf(config)# access-list acl_test permit tcp any host 10.16.17.202 eq 80
gandalf(config)# access-list acl_test permit icmp any any
gandalf(config)# access-list acl_test deny ip any any
gandalf(config)# show access-list acl_test
access-list acl_test; 5 elements
access-list acl_test line 1 permit tcp any host 10.16.17.202 eq ssh (hitcnt=0)
access-list acl_test line 2 permit tcp any host 10.16.17.202 eq smtp (hitcnt=0)
access-list acl_test line 3 permit tcp any host 10.16.17.202 eq www (hitcnt=0)
access-list acl_test line 4 permit icmp any any (hitcnt=0)
access-list acl_test line 5 deny ip any any (hitcnt=0)
Knowledge of the command set is critical to effectively configure a firewall through a
CLI. Many vendors (and third parties) have worked hard to reduce the configuration of a
firewall to a more simplistic method. When the initial configuration is done (supplying
the firewall software with an IP address and net mask), the end user can immediately
switch to a more graphical method of configuring the firewall.
Managing Firewalls with a GUI
A GUI provides a more-user-friendly interface to configure the firewall. Some firewalls
are configured through a direct interface on the host, such as Symantec Norton Internet
Security shown in Figure 11-1
and Figure 11-2, before the firewall is active. Some come
with a preconfigured IP address and an administrative password to be used for access by
the end user during initial configuration (such as Linksys or the PIX 501 and 506E series
systems).
Figure 11-1. Symantec Internet Security Configuration
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Figure 11-2. Symantec Firewall Configuration
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The PIX Device Manager (for PIX operating systems up to versions 6.3(5)), known as the
Cisco Adaptive Security Device Manager in PIX version 7.0, is a Java applet that is
downloaded from the PIX or ASA device and runs locally through the client browser.
Figure 11-3
shows the PIX Device Manager screen.
Figure 11-3. Cisco PIX Device Manager
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The information is presented in a more natural fashion to the end user in the form of
graphics and graphs for performance.
N
ot to be outdone, there are GUIs for Linux's IPTables firewall software. Some are web
based (such as Webmin), and some are applications running on the Linux system itself
(such as Firestarter or FW-Builder). Firestarter provides a simple, easy-to-use interface
for IPTables, as shown in Figure 11-4
.
Figure 11-4. Firestarter for IPTables
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Webmin provides a method by which the firewall can be managed through a web browser
interface, which is more convenient than an application that can only be viewed on an X
Windows-enabled server. Figure 11-5
shows this interface.
Figure 11-5. Webmin IPTables Rules Interface
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Interface Preference
Whether it is through a CLI or through a GUI, the management of a firewall can range
from the highly complex to the relatively easy. Typically, novice users start by
administering the firewall through a GUI. Over time, as their experience level and
comfort level with the firewall increase, they may find it more convenient to use a CLI.
One significant benefit of a CLI over a GUI is that the CLI is available through Telnet
and SSH sessions as well as connected directly to the serial port. This becomes important
when considering how access to the firewallmanagementinterface will be controlled.
.
Firewall Management Interface
Modern firewalls come with two administrative interfaces:
• The CLI
• The GUI (typically,.
Managing Firewalls with a GUI
A GUI provides a more-user-friendly interface to configure the firewall. Some firewalls
are configured through a direct interface