Adversaries may use masquerading to disguise a malicious application or executable as another file, to avoid operator and engineer suspicion. Possible disguises of these masquerading files can include commonly found programs, expected vendor executables and configuration files, and other commonplace application and naming conventions. By impersonating expected and vendor-relevant files and applications, operators and engineers may not notice the presence of the underlying malicious content and possibly end up running those masquerading as legitimate functions. Applications and other files commonly found on Windows systems or in engineering workstations have been impersonated before. This can be as simple as renaming a file to effectively disguise it in the ICS environment.
Stuxnet renames s7otbxdx.dll, a dll responsible for handling communications with a PLC. It replaces this dll file with its own version that allows it to intercept any calls that are made to access the PLC. 
Require signed binaries.
Use tools that restrict program execution via application control by attributes other than file name for common system and application utilities.
|M0922||Restrict File and Directory Permissions||
Use file system access controls to protect system and application folders.
|ID||Data Source||Data Component|
|DS0003||Scheduled Job||Scheduled Job Metadata|
|Scheduled Job Modification|