Starting with SP5, you can disable ICMP redirects, to prevent a denial of service attack, by using Regedt32 to navigate to:

HKEY_LOCAL_MACHINE\System\Currentcontrolset\Services\Tcpip\Parameters

On the Edit menu, Add Value name EnableICMPRedirects, a type REG_DWORD entry, and set the data value to 0. A data value of 1 enables ICMP redirects.

NOTE: See Q195686 - Explanation of ICMP Redirect Behavior.