System firmware on modern assets is often designed with an update feature. Older device firmware may be factory installed and require special reprograming equipment. When available, the firmware update feature enables vendors to remotely patch bugs and perform upgrades. Device firmware updates are often delegated to the user and may be done using a software update package. It may also be possible to perform this task over the network.

An adversary may exploit the firmware update feature on accessible devices to upload malicious or out-of-date firmware. Malicious modification of device firmware may provide an adversary with root access to a device, given firmware is one of the lowest programming abstraction layers.^[1]

References

1. Basnight, Zachry, et al. 2013 Retrieved. 2017/10/17

Adversaries may install malicious or vulnerable firmware onto modular hardware devices. Control system devices often contain modular hardware devices. These devices may have their own set of firmware that is separate from the firmware of the main control system equipment.

This technique is similar to System Firmware, but is conducted on other system components that may not have the same capabilities or level of integrity checking. Although it results in a device re-image, malicious device firmware may provide persistent access to remaining devices.^[1]

An easy point of access for an adversary is the Ethernet card, which may have its own CPU, RAM, and operating system. The adversary may attack and likely exploit the computer on an Ethernet card. Exploitation of the Ethernet card computer may enable the adversary to accomplish additional attacks, such as the following:^[1]

• Delayed Attack - The adversary may stage an attack in advance and choose when to launch it, such as at a particularly damaging time.
• Brick the Ethernet Card - Malicious firmware may be programmed to result in an Ethernet card failure, requiring a factory return.
• Random Attack or Failure - The adversary may load malicious firmware onto multiple field devices. Execution of an attack and the time it occurs is generated by a pseudo-random number generator.
• A Field Device Worm - The adversary may choose to identify all field devices of the same model, with the end goal of performing a device-wide compromise.
• Attack Other Cards on the Field Device - Although it is not the most important module in a field device, the Ethernet card is most accessible to the adversary and malware. Compromise of the Ethernet card may provide a more direct route to compromising other modules, such as the CPU module.

References

1. Daniel Peck, Dale Peterson 2009, January 28 Leveraging Ethernet Card Vulnerabilities in Field Devices Retrieved. 2017/12/19