How to break plc password?

if you are talking about allen bradly then i hae a trick...you need to PM me..its sure you will not fail

I THINK THIS IS IMPOSSIBLE TO BREAK PASSWORD OF PLC, JUST SWITCH OFF THE SYSTEM

Different Software utilities available for break different brands of Plc but it is not legal so avoid it is better. 

PLC Omron C series are very easy to crack password, New version is too difficult but it'll not able to crack. You can get more detail at : http://tuanlongtai.blogspot.com/

Many of the PLC password protection can be removed by removing the Battery and remove the power for some specific time.In most of the cases the protection removed, if the protection still present then rmove the processor (in PLCs where  Controller connection to base board through the FPGA slot) for some time. Problem solved. Thanks

This answer is depend upon my experience. You can clear the memory by removing battery so there is nothing in the PLC, but there is no way to access a password protected program