Detecting Brute-Force and Dictionary attacks

Hi All,  

I am looking for a good tool to detect brute-force and dictionary attacks on user accounts on a Linux system . The tool should also have the intelligence to differntiate between user mistakes and actual brute-force/dictionary attacks and reduce the false positives. SuSE/RedHat included security tools are not helping in this case . 

Please , anyone knows any third party security tool or any opensource security  tool which solves my problem ?

Thanks & Regards,
Shashi Kanth,CISSP