Protect and control software stored

It's been said for every measure, there's a countermeasure, and that's also true for securing code in embedded systems. Sometimes a small device can be just the countermeasure needed to thwart cloning of flash contents.

Many systems use external standard flash memory chip(s) to store the operating program for processors that do not include embedded nonvolatile program storage. This is great because it allows easy flash memory expansion and software modification, perhaps in the manufacturing line as a customer download or during a maintenance operation. The downside is that the OEM loses control over the contents of the flash, potentially allowing unauthorized copies or modification.

Refer:
http://embedded-computing.com/articles/protect-control-software-stored-flash-memory/#at_pco=cfd-1.0