User's Manual 14. Security
Version 4.4.0 255 MP26x/MP27x
You can choose from among three pre-defined security levels for the device: Minimum,
Typical, and Maximum (the default setting). The table below summarizes the behavior of
the device for each of the three security levels.
Table 14-1: Behavior for the Three Security Levels
Security Level Requests Originating
in the WAN
(Incoming Traffic)
Requests
Originating
in the LAN
(Outgoing Traffic)
Maximum
Security
(Default)
Blocked: No access to home network
from Internet, except as configured in
the Local Servers, DMZ host and
Remote Access screens
Limited: Only commonly- used services,
such as Web- browsing and e-mail, are
permitted
Typical Security
Blocked: No access to home network
from Internet, except as configured in
the Local Servers, DMZ host and
Remote Access screens
Unrestricted: All services are permitted,
except as configured in the Access
Control screen
Minimum
Security
Unrestricted: Permits full access from
Internet to home network; all connection
attempts permitted.
Unrestricted: All services are permitted,
except as configured in the Access
Control screen
These services include Telnet, FTP, HTTP, HTTPS, DNS, IMAP, POP3 and SMTP.
The list of allowed services at 'Maximum Security' mode can be edited in the screen's
'Access Control on page 256'.
Some applications (such as some Internet messengers and Peer-To-Peer client
applications) tend to use these ports if they cannot connect with their own default ports.
When applying this behavior, these applications are not blocked outbound, even at
Maximum Security Level.
To configure the device's security settings:
(See the figure 'General Security Level Settings' on page 254.)
1. Choose from among the three predefined security levels described in the table above.
'Maximum Security' is the default setting.
Using the Minimum Security setting may expose the home network to
significant security risks, and thus should only be used, when necessary, for
short periods of time.
2. Check the 'Block IP Fragments' check box to protect your home network from a
common type of hacker attack that could make use of fragmented data packets to
sabotage your home network. Note that some UDP-based services make legitimate
use of IP fragments. You need to allow IP fragments to pass into the home network to
make use of these select services.
3. In the 'TCP Session timeout' field, enter the time-to-live (TTL) in units of seconds for
TCP sessions. The valid range is 1 to 3600 hours (default is an hour).
4. Click OK to save the changes.
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