Modify Authentication Process: Network Device Authentication
Adversaries may use Patch System Image to hard code a password in the operating system, thus bypassing of native authentication mechanisms for local accounts on network devices.
Modify System Image may include implanted code to the operating system for network devices to provide access for adversaries using a specific password. The modification includes a specific password which is implanted in the operating system image via the patch. Upon authentication attempts, the inserted code will first check to see if the user input is the password. If so, access is granted. Otherwise, the implanted code will pass the credentials on for verification of potentially valid credentials.
Use multi-factor authentication for user and privileged accounts. Most embedded network devices support TACACS+ and/or RADIUS. Follow vendor prescribed best practices for hardening access control. 
|Privileged Account Management||
Restrict administrator accounts to as few individuals as possible, following least privilege principles. Prevent credential overlap across systems of administrator and privileged accounts, particularly between network and non-network platforms, such as servers or endpoints.
Detection of this behavior may be difficult, detection efforts may be focused on closely related adversary behaviors, such as Modify System Image.