To prevent synattack in Windows server 2003 please follow this-

Save the following in synattackprotect.reg and double click it to merge-

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
“EnableTCPChimney”=dword:00000000
“SynAttackProtect”=dword:00000002
“TcpMaxHalfOpen”=dword:00000064
“TcpMaxHalfOpenRetried”=dword:00000050
“TcpMaxPortsExhausted”=dword:00000005
“TcpMaxConnectResponseRetransmissions”=dword:00000003