This detection rule monitors for failed logon attempts to Microsoft SQL Server (MSSQL) from client machines. It is specifically designed to capture instances where the logon provider name contains 'MSSQL' and the logon event corresponds to Event ID 18456, which indicates that the server could not open the specified database because the logon failed. The rule's configuration requires the MSSQL authentication log to be enabled for the event to be captured correctly. This rule can aid in identifying potential unauthorized access attempts or misconfigurations related to database access. The alert level for this detection is classified as low, indicating that while failed logons can indicate malicious behavior, they can also result from legitimate scenarios such as password changes or misconfigured automated jobs. The author suggests monitoring the context of such events to differentiate between benign and malicious activities.