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Friday, October 10, 2008

Harden the TCP/IP Stack...

... for Denial of Service Attacks (Windows 2000/XP)
Source December 19, 2002
Denial of service attacks are network attacks that are aimed at making a computer or a particular service unavailable to network users.
These settings can be used to increase the ability for Windows to defend against these attacks when connected directly to the Internet.

This tweak can be easily applied using WinGuides Tweak Manager.
Download a free trial now!
Open your registry and find the key below.

Create the following DWORD values and set them according to the table below.

  • EnableDeadGWDetect = "0" (default = 1)
    Disables dead-gateway detection as an attack could force the server to switch gateways.
  • EnableICMPRedirect = "0" (default = 1)
    Stops Windows from altering its route table in response to ICMP
    redirect messages. Some documentation has this listed as
    "EnableICMPRedirects" but according to Microsoft it should be
    "EnableICMPRedirect" no "s".
  • EnablePMTUDiscovery = "0" (default = 1)
    Disables maximum transmission unit (MTU) discovery as an attacker
    could force the MTU value to a very small value and overwork the stack.
  • KeepAliveTime = "300,000" (default = 7,200,000)
    Reduces how often TCP attempts to verify that an idle connection is still intact by sending a keep-alive packet.
  • NoNameReleaseOnDemand = "1" (default = 0)
    Protects the computer against malicious NetBIOS name-release attacks.
  • PerformRouterDiscovery = "0" (default = 1)
    Disables ICMP Router Discovery Protocol (IRDP) where an an attacker may remotely add default route entries on a remote system.
  • SynAttackProtect = "2" (default = 0)
    Automatically adds additional delays to connection indications, and
    TCP connection requests quickly timeout when a SYN attack is in
Restart Windows for the changes to take effect.
These values will not give the best performance due
to additional checking and less optimization, but they will provide
greater protection against attacks.

Registry Editor Example
|(Default)REG_SZ(value not set)|
|EnableDeadGWDetectREG_DWORD0x00000000 (0)|
|EnableICMPRedirectREG_DWORD0x00000000 (0)|
|EnablePMTUDiscoveryREG_DWORD0x00000000 (0)|
|KeepAliveTimeREG_DWORD0x000493e0 (300000)|
|NoNameReleaseOnDemandREG_DWORD0x00000001 (1)|
|PerformRouterDiscoveryREG_DWORD0x00000000 (0)|
|SynAttackProtectREG_DWORD0x00000002 (2)|

Registry Settings
System Key: [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
Value Name:
EnableDeadGWDetect, EnableICMPRedirect, EnablePMTUDiscovery,KeepAliveTime, NoNameReleaseOnDemand, PerformRouterDiscovery,SynAttackProtect
Data Type: REG_DWORD (DWORD Value)

Disclaimer: Modifying the registry can cause serious problems that may require you to reinstall your operating system. We cannot guarantee that problems resulting from modifications to the registry can be solved. Use the information provided at your own risk.

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