101
In the SCE UI, these options appear as:
•
Enabled
•
Disabled
•
Not Defined
Potential Impact:
The impact should be small if administrators implement the other settings as
suggested in this section, but as stated in the previous item,
DynamicBacklogGrowthDelta,
setting the
values improperly could lead to diminished responsiveness or a DoS condition.
MinimumDynamicBacklog: (AFD MinimumDynamicBacklog) Minimum
number of free connections for Winsock applications (20 recommended
for systems under attack, 10 otherwise)
This entry appears as
MSS: (AFD MinimumDynamicBacklog) Minimum number of free connections for
Winsock applications (20 recommended for systems under attack, 10 otherwise)
in the SCE. This
setting controls the minimum number of free connections allowed on a listening endpoint. If the
number of free connections drops below this value, then a thread is queued to create additional free
connections. This value should not be too large, as the dynamic backlog code engages whenever the
number of free connections falls below this value. Too large a value may lead to a performance
reduction.
Vulnerability:
Socket applications may be susceptible to DoS attacks.
Countermeasure:
Configure
MSS: (AFD MinimumDynamicBacklog) Minimum number of free
connections for Winsock applications (20 recommended for systems under attack, 10 otherwise)
to a
value of
10
.
The possible values for this Registry value are:
•
1
to
0xFFFFFFFF
; default is
0
In the SCE UI, this appears as a text entry box:
•
A user defined number
•
Not Defined
Potential Impact:
Setting this value to too large a number could cause a large amount of system
resources to be assigned to allocating additional free connections that may not actually be needed.
This could lead to poor performance or a DoS condition.
MaximumDynamicBacklog: (AFD MaximumDynamicBacklog) Maximum
number of ’quasi-free’ connections for Winsock applications
This entry appears as
MSS: (AFD MaximumDynamicBacklog) Maximum number of ’quasi-free’
connections for Winsock applications
in the SCE. This setting controls the maximum number of "quasi-
free" connections allowed on a listening endpoint. Quasi-free connections include the number of free
connections plus those connections in a half-connected (SYN_RECEIVED) state. No attempt is made to
create additional free connections if doing so would exceed this value.
Vulnerability:
Socket applications may be susceptible to DoS attacks.