Event ID: 17806 - Attack on SQL Server

Hi,
I see the following event error : failure attempt to access my SQL Server by
some hacker.
Source: MS SQL Server
Event ID: 17806
SSPI handshake failed with error code 0x8009030c while establishing a
connection with integrated security; the connection has been closed.
What preventive measures i can take ?
Please help.
Message posted via droptable.com
http://www.droptable.com/Uwe/Forums.aspx/sql-server/200707/1
What make you think this is a hacker?
Is youre db connected with iis on the internet?
Most companies get more then 10.000 hack attemps a day ;)
Just make sure you got the latest security updates --run security baseline
analyser on youre pc to scan for leaks.
If somebody is doing a attack(SQL injection) you should see multiple login
failed messages attempts in youre logs.
Cheers