99
In the SCE UI, these options appear as:
•
Enabled
•
Disabled
•
Not Defined
Potential Impact:
Disabling this setting prevents Windows Server 2003, which supports the IRDP,
from automatically detecting and configuring Default Gateway addresses on the computer.
TCPMaxPortsExhausted: How many dropped connect requests to initiate
SYN attack protection (5 is recommended)
This entry appears as
MSS: How many dropped connect requests to initiate SYN attack protection (5 is
recommended)
in the SCE. This parameter controls the point at which SYN-ATTACK protection starts
to operate. SYN-ATTACK protection begins to operate when
TcpMaxPortsExhausted
connect requests
have been refused by the system because the available backlog for connections is set at 0.
Vulnerability:
In a SYN flood attack, the attacker sends a continuous stream of SYN packets to a
server, and the server leaves the half-open connections open until it is overwhelmed and no longer is
able to respond to legitimate requests.
Countermeasure:
Configure
MSS: How many dropped connect requests to initiate SYN attack
protection (5 is recommended)
to a value of
5
. The possible values for this Registry value are:
•
0
to
0xFFFF
; default is
5
In the SCE UI, this appears as a text entry box:
•
A user defined number
•
Not Defined
Potential Impact:
This parameter controls the point at which SYN-ATTACK protection starts to
operate. SYN-ATTACK protection begins to operate when
TCPMaxPortsExhausted
connect requests
have been refused by the system because the available backlog for connections is set at 0. This
should have little impact on the server or systems attempting to use it in a legitimate manner.
2.8.6.2
AFD.SYS settings
Windows Sockets applications such as File Transfer Protocol (FTP) servers and Web servers have their
connection attempts handled by Afd.sys. Afd.sys has been modified to support large numbers of
connections in the half-open state without denying access to legitimate clients. This is accomplished by
allowing the administrator to configure a dynamic backlog. The version of Afd.sys included with
Windows Server 2003 supports four registry parameters that can be used to control the dynamic
backlog behavior. The following registry value entries have been added to the template file in the
following registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\AFD\Parameters\