SQL Server 2000 is accessed through the network, either through a named pipe or a network protocol, such as TCP. For this reason, a SQL Server deployment has to be set up to accept connections only from trusted sources. If you're running SQL Server on only one machine (possibly in conjunction with a Web server on the same box), then you'll want to make sure it's only accessible to that machine and not to unauthorized remote clients who may try to connect.
Even when SQL Server 2000 only uses named pipes as its network protocol, it can still be accessed from the outside world if the host server does not block connections from UDP port 1434. SQL Server listens on UDP port 1434 for a handshake (a packet payload of value 0x02) and then replies with detailed information about all the available instances of SQL Server on that computer. This includes the names of the server instances, the network connections (such as named pipe info) and the version(s) of SQL Server running. This is obviously a major problem!
To help combat this problem, a team of programmers from the SQLSecurity.com site created SQLPing, a simple command-line tool to determine if a given machine has its SQL Server listening port open for public access. The program is simple enough: Invoke it from the command line with either an IP address or a hostname, and it will attempt to contact UDP port 1434 on the target machine and report any results returned.
If you run SQLPing across the Internet and are able to retrieve information from a given SQL Server, that box should be locked down as soon as possible. Block UDP port 1434 wherever possible, or simply set up an appropriate firewall and only open ports as needed. Even if that instance of SQL Server isn't set to accept connections from the Internet at large, the information revealed can be used in other contexts.
About the author: Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter. Check out his Windows 2000 blog for his latest advice and musings on the world of Windows network administrators – please share your thoughts as well!
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