SQL Profiler, included with Microsoft SQL Server, is commonly used to audit connections to the server. However, Imperva Inc. discovered that login names prefixed with null characters aren't visible to the profiling tool in SQL Server 2000. Microsoft said that the problem is fixed in SQL Server 2005.
The Microsoft article "BUG: Login names that contain leading zero characters are not visible when you use SQL Profiler to audit connections to SQL Server 2000" explains that the problem also exists when using certain stored procedures to monitor connections. The article also offers workaround information.