Customizing MS.SQL.Login.Brute.Force

Hello,

I want to customize the MS.SQL.Login.Brute.Force signature to adjust the frecuency. The standard signature fires when 5 MS SQL login failures within a short period of time 1 second between a unique pair of hosts. I know that I have to create a custom signature, but I don't know as I have to find the pattern...

I have started with this rule...

F-SBID( --attack_id 7171; --name "My.MS.SQL.Login.Brute.Force"; --protocol TCP; --dst_port 1433; --flow from_client; --rate 5,1800; --track SRC_IP ; )

Somebody can help me, please?

Thanks