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Disabling Netbios
Windows networks use a system of shared files and printers based upon the
SMB (Shared Message Block) protocol. This protocol is deployed within the
Windows NetBIOS protocol, which in turn, is installed by default over
TCP/IP in the first versions of Windows95 and Windows 3.11 for Group Work.
This characteristic becomes a security problem when systems using Windows
networking shares connect to an unreliable network such as the Internet.
In such cases, any Internet user can attempt to access the Windows system
NetBIOS services remotely through
the TCP/IP and access the resources if these have not been adequately protected.
There is the possibility that in certain local network configurations it
may be necessary to install NetBIOS over TCP/IP and in order to counteract
the security problem, it becomes essential to establish password accesses
to all shared resources. This
way, a user outside the system will not know the password and therefore
will be unable to access such resources from outside the system.
In order to check if you have NetBIOS installed over TCP/IP in your Win9x
system, look up its properties in (Start -> Configuration -> Control Panel
-> Network -> TCP/IP -> Properties -> NetBIOS tab), where there is a check
box that allows
you to disable it. This prevents an Internet user from accessing shared
resources on the local network. Another way of checking whether we are
exporting NetBIOS to the Internet is to launch the command NETSTAT -A (in
MS-DOS) and see if the ports 137, 138 and 139 appear.
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