Block Reporting Message

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Block Reporting Message
Technique
ID T0804
Tactic Inhibit Response Function
Data Sources Alarm History, Data historian, Network protocol analysis, Packet capture
Asset Field Controller/RTU/PLC/IED, Input/Output Server

Description

Adversaries may block or prevent a reporting message from reaching its intended target. In control systems, reporting messages contain telemetry data (e.g., I/O values) pertaining to the current state of equipment and the industrial process. By blocking these reporting messages, an adversary can potentially hide their actions from an operator.

Blocking reporting messages in control systems that manage physical processes may contribute to system impact, causing inhibition of a response function. A control system may not be able to respond in a proper or timely manner to an event, such as a dangerous fault, if its corresponding reporting message is blocked.1

In the 2015 attack on the Ukranian power grid, malicious firmware was used to render communication devices inoperable and effectively block messages from being reported.2


Procedure Examples

  • Industroyer uses the first COM port from the configuration file for the communication and the other two COM ports are opened to prevent other processes accessing them. This may block processes or operators from getting reporting messages from a device.3

Mitigations

  • Network Allowlists - Utilize network allowlists to restrict unnecessary connections to network devices (e.g., comm servers, serial to ethernet converters) and services, especially in cases when devices have limits on the number of simultaneous sessions they support.
  • Out-of-Band Communications Channel - Provide an alternative method for sending critical report messages to operators, this could include using radio/cell communication to obtain messages from field technicians that can locally obtain telemetry and status data.
  • Static Network Configuration - Unauthorized connections can be prevented by statically defining the hosts and ports used for automation protocol connections.