星期四, 10月 12, 2006

What's port 445 used for in Windows 2000/XP?

Among the new ports used by Windows 2000, Windows XP and Windows Server 2003, is TCP port 445 which is used for SMB over TCP.
The SMB (Server Message Block) protocol is used among other things for file sharing in Windows NT/2000/XP. In Windows NT it ran on top of NetBT (NetBIOS over TCP/IP), which used the famous ports 137, 138 (UDP) and 139 (TCP). In Windows 2000/XP/2003, Microsoft added the possibility to run SMB directly over TCP/IP, without the extra layer of NetBT. For this they use TCP port 445.
At its simplest NetBIOS on your LAN may just be a necessary evil. NetBIOS on your WAN or over the Internet, however, is an enormous security risk. All sorts of information, such as your domain, workgroup and system names, as well as account information is obtainable via NetBIOS. It really is in your best interests to ensure that NetBIOS never leaves your network.
If you are using a router as your Internet gateway then you will want to ensure that it does not allow inbound or outbound traffic via TCP ports 135-139.
If you're using a Firewall then you should also block the same ports - TCP ports 135-139.
If you are using a multi-homed machine i.e. more than 1 network card, then you should disable NetBIOS on every network card, or Dial-Up Connection under the TCP/IP properties, that is not part of your local network.

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香港,夕陽

「夕陽之歌」,反映了此時此刻很多香港人的心情。 幾代人的集體回憶,不會如此容易消失。 真香港人,不會如同雲一般消失,但會be water!