Adversaries with privileged network access may seek to modify network traffic in real time using adversary-in-the-middle (AiTM) attacks. (Citation: Gabriel Sanchez October 2017) This type of attack allows the adversary to intercept traffic to and/or from a particular device on the network. If a AiTM attack is established, then the adversary has the ability to block, log, modify, or inject traffic into the communication stream. There are several ways to accomplish this attack, but some of the most-common are Address Resolution Protocol (ARP) poisoning and the use of a proxy. (Citation: Bonnie Zhu, Anthony Joseph, Shankar Sastry 2011) An AiTM attack may allow an adversary to perform the following attacks: [Block Reporting Message](https://attack.mitre.org/techniques/T0804), [Spoof Reporting Message](https://attack.mitre.org/techniques/T0856), [Modify Parameter](https://attack.mitre.org/techniques/T0836), [Unauthorized Command Message](https://attack.mitre.org/techniques/T0855)
Architect sections of the network to isolate critical systems, functions, or resources. Use physical and logical segmentation to prevent access to potentially sensitive systems and information. Use a DMZ to contain any internet-facing services that should not be exposed from the internal network. Restrict network access to only required systems and services. In addition, prevent systems from other networks or business functions (e.g., enterprise) from accessing critical process control systems. For example, in IEC 62443, systems within the same secure level should be grouped into a zone, and access to that zone is restricted by a conduit, or mechanism to restrict data flows between zones by segmenting the network. (Citation: IEC February 2019) (Citation: IEC August 2013)
M0931Network Intrusion PreventionUse intrusion detection signatures to block traffic at network boundaries. In industrial control environments, network intrusion prevention should be configured so it will not disrupt protocols and communications responsible for real-time functions related to control or safety.
Configure hosts and devices to use static network configurations when possible, protocols that require dynamic discovery/addressing (e.g., ARP, DHCP, DNS) can be used to manipulate network message forwarding and enable various AiTM attacks. This mitigation may not always be usable due to limited device features or challenges introduced with different network configurations.
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