C
ONFIGURING THE
 B
ARRICADE
4-38
Stateful Packet 
Inspection
Enabled This option allows you to select different 
application types that are using dynamic port 
numbers. If you wish to use Stateful Packet 
Inspection (SPI) for blocking packets, click on the 
Yes radio button in the “Enable SPI and Anti-DoS 
firewall protection” field and then check the 
inspection type that you need, such as Packet 
Fragmentation, TCP Connection, UDP Session, 
FTP Service and TFTP Service.
It is called a “stateful” packet inspection because it 
examines the contents of the packet to determine 
the state of the communication; i.e., it ensures that 
the stated destination computer has previously 
requested the current communication. This is a 
way of ensuring that all communications are 
initiated by the recipient computer and are taking 
place only with sources that are known and trusted 
from previous interactions. In addition to being 
more rigorous in their inspection of packets, 
stateful inspection firewalls also close off ports 
until a connection to the specific port is requested.
When particular types of traffic are checked, only 
the particular type of traffic initiated from the 
internal LAN will be allowed. For example, if the 
user only checks FTP Service in the Stateful Packet 
Inspection section, all incoming traffic will be 
blocked except for FTP connections initiated from 
the local LAN.
When hackers 
attempt to enter 
your network, 
we can alert you 
by email
Your E-mail 
Address
Enter your email address.
SMTP Server 
Address
Enter your SMTP server address (usually the part 
of the email address following the “@” sign).
POP3 Server 
Address
Enter your POP3 server address (usually the part 
of the email address following the “@” sign).
User Name Enter your email account user name.
Parameter Defaults Description