3Com 3C16111 - SuperStack 3 Firewall Web Site Filter, Руководство пользователя

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100 C
HAPTER
7: S
ETTING A
P
OLICY
HTTP protocol even if both NetBIOS Passthrough boxes are left
unchecked.
Enabling Stealth
Mode
By default, the Firewall responds to incoming connection requests as
either
blocked or open . If you check the box to enable Stealth Mode and
click on the Update button, no response will be made to inbound
requests, which makes your network invisible to potential attackers.
Allowing Fragmented
Packets
By default the Firewall drops fragmented packets as they may form part
of a Denial of Service attack. Fragmented packets can occur naturally as
part of a congested network and you may want to allow them to increase
the throughput of your Firewall.
Fragmented packets that are dropped will show as entries in the Firewall
Log. See “Viewing the Log” on page 80 for details.
Allow Fragmented Packets over PPTP/IPSec
Point-to-point Tunneling Protocol (PPTP) and IPSec are forms of VPN that
allows data to pass through the Firewall without termination. In some
cases, passing large amounts of data through the Firewall can cause
packets to become fragmented which results in low data throughput.
If fragmented PPTP packets are being blocked check the Over PPTP box. If
fragmented IPSec packets are being blocked check the Over IPSec box.
Setting the Network Connection Inactivity Timeout
If a connection to a server outside the LAN remains idle for more than 5
minutes (default value), the Firewall closes the connection. This is done
for security purposes. Without this timeout, it is possible that connections
could stay open indefinitely, creating potential security risks. You can
increase the timeout interval if users frequently complain of dropped
connections in applications such as Telnet and FTP.
Click Update to save your changes.
You must restart the Firewall for these changes to take effect.
DUA1611-0AAA02.book Page 100 Thursday, August 2, 2001 4:01 PM