T1693.001: System Firmware

Access Management technologies can be used to enforce authorization polices and decisions, especially when existing field devices do not provide sufficient capabilities to support user identification and authentication. (Citation: McCarthy, J et al. July 2018) These technologies typically utilize an in-line network device or gateway system to prevent access to unauthenticated users, while also integrating with an authentication service to first verify user credentials. (Citation: Centre for the Protection of National Infrastructure November 2010)

Require user authentication before allowing access to data or accepting commands to a device. While strong multi-factor authentication is preferable, it is not always feasible within ICS environments. Performing strong user authentication also requires additional security controls and processes which are often the target of related adversarial techniques (e.g., Valid Accounts, Default Credentials). Therefore, associated ATT&CK mitigations should be considered in addition to this, including [Multi-factor Authentication](https://attack.mitre.org/mitigations/M0932), [Account Use Policies](https://attack.mitre.org/mitigations/M0936), [Password Policies](https://attack.mitre.org/mitigations/M0927), [User Account Management](https://attack.mitre.org/mitigations/M0918), [Privileged Account Management](https://attack.mitre.org/mitigations/M0926), and [User Account Control](https://attack.mitre.org/mitigations/M1052).

Enforce binary and application integrity with digital signature verification to prevent untrusted code from executing.

Require the authentication of devices and software processes where appropriate. Devices that connect remotely to other systems should require strong authentication to prevent spoofing of communications. Furthermore, software processes should also require authentication when accessing APIs.

Utilize strong cryptographic techniques and protocols to prevent eavesdropping on network communications.

Use secure methods to boot a system and verify the integrity of the operating system and loading mechanisms.

Perform regular software updates to mitigate exploitation risk. Software updates may need to be scheduled around operational down times.

Protect sensitive data-at-rest with strong encryption.

Network allowlists can be implemented through either host-based files or system hosts files to specify what connections (e.g., IP address, MAC address, port, protocol) can be made from a device. Allowlist techniques that operate at the application layer (e.g., DNP3, Modbus, HTTP) are addressed in [Filter Network Traffic](https://attack.mitre.org/mitigations/M0937) mitigation.

Perform audits or scans of systems, permissions, insecure software, insecure configurations, etc. to identify potential weaknesses. Perform periodic integrity checks of the device to validate the correctness of the firmware, software, programs, and configurations. Integrity checks, which typically include cryptographic hashes or digital signatures, should be compared to those obtained at known valid states, especially after events like device reboots, program downloads, or program restarts.

When communicating over an untrusted network, utilize secure network protocols that both authenticate the message sender and can verify its integrity. This can be done either through message authentication codes (MACs) or digital signatures, to detect spoofed network messages and unauthorized connections.