[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"ForwardBroadcasts"=dword:00000000
"IPEnableRouter"=dword:00000000
"Domain"=""
"SearchList"=""
"UseDomainNameDevolution"=dword:00000001
"EnableICMPRedirect"=dword:00000001
"DeadGWDetectDefault"=dword:00000001
"DontAddDefaultGatewayDefault"=dword:00000000
"EnableSecurityFilters"=dword:00000000
"AllowUnqualifiedQuery"=dword:00000000
"PrioritizeRecordData"=dword:00000001
"ReservedPorts"=hex(7):31,00,34,00,33,00,33,00,2d,00,31,00,34,00,33,00,34,00,\
  00,00,00,00
"DisableTaskOffload"=dword:00000001
"DefaultTTL"=dword:00000040
"TcpRecvSegmentSize"=dword:000005b4
"GlobalMaxTcpWindowSize"=dword:00002000
"TcpWindowSize"=dword:00002000
"EnablePMTUDiscovery"=dword:00000000
"EnablePMTUBHDetect"=dword:00000001
"SackOpts"=dword:00000001
"Tcp1323Opts"=dword:00000003
"SynAttackProtect"=dword:00000002
"TcpMaxConnectResponseRetransmissions"=dword:00000001
"TcpMaxPortsExhausted"=dword:00000005
"TcpMaxHalfOpen"=dword:000001f4
"TcpMaxHalfOpenRetried"=dword:00000190
"KeepAliveTime"=dword:00007530
"TcpTimedWaitDelay"=dword:0000001e

如是80端口被SYN，请参考以上注册表信息，不能完全杜绝，但是有一定效果