FAQ02639 of Programmable Controllers FAQ

Individual tasks can be protected when using a CS1/CJ1-series CPU Unit with unit Ver.2.0 or later and with CX-Programmer FA Integrated Tool Package Ver.4.0 or higher.
Single or multiple tasks (programs) can be password protected, preventing them from being read or modified, which makes it possible to prevent knowledge from being leaked about a specific task.

When using a Programmable Controller with unit version earlier than 2.0 or a CX-Programmer version lower than 4.0, individual tasks cannot be protected, so the entire program must be protected instead.