GEN:SID 1:680
Message MS-SQL/SMB sa login failed
Summary This event is generated when a command is issued to an SQL database server that may result in a serious compromise of the data stored on that system.
Impact Serious. An attacker may have gained administrator access to the system.
Detailed Information This event is generated when an attacker issues a special command to an SQL database that may result in a serious compromise of all data stored on that system.

Such commands may be used to gain access to a system with the privileges of an administrator, delete data, add data, add users, delete users, return sensitive information or gain intelligence on the server software for further system compromise.

This connection can either be a legitimate telnet connection or the result of spawning a remote shell as a consequence of a successful network exploit.
Affected Systems  
Attack Scenarios Simple. These are SQL database commands.
Ease of Attack Simple.
Corrective Action Disallow direct access to the SQL server from sources external to the protected network.

Ensure that this event was not generated by a legitimate session then investigate the server for signs of compromise

Look for other events generated by the same IP addresses.
Additional References  
Rule References bugtraq: 4797
cve: 2000-1209