T0878_alarm-suppression

DevOps & Security

Adversaries may target protection function alarms to prevent them from notifying operators of critical conditions.

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T0878 Alarm Suppression

High-Level Description

Adversaries may target protection function alarms to prevent them from notifying operators of critical conditions. Alarm messages may be a part of an overall reporting system and of particular interest for adversaries. Disruption of the alarm system does not imply the disruption of the reporting system as a whole.

A Secura presentation on targeting OT notes a dual fold goal for adversaries attempting alarm suppression: prevent outgoing alarms from being raised and prevent incoming alarms from being responded to. The method of suppression may greatly depend on the type of alarm in question:

An alarm raised by a protocol message
An alarm signaled with I/O
An alarm bit set in a flag (and read)

In ICS environments, the adversary may have to suppress or contend with multiple alarms and/or alarm propagation to achieve a specific goal to evade detection or prevent intended responses from occurring. Methods of suppression may involve tampering or altering device displays and logs, modifying in memory code to fixed values, or even tampering with assembly level instruction code.

Kill Chain Phase

Inhibit Response Function (TA0107)

Platforms: ICS

What to Check

Identify if Alarm Suppression technique is applicable to target ICS environment
Check ICS/SCADA systems for indicators of Alarm Suppression
Verify mitigations are bypassed or absent (4 known mitigations)
Assess detection coverage (1 detection strategies)

How to Test

Identify Attack Surface

Determine if the target ICS/SCADA environment is susceptible to Alarm Suppression by examining operational technology systems and network architecture.

Assess Existing Defenses

Review whether mitigations for T0878 are in place. If defenses are absent or misconfigured, this technique may be exploitable in the ICS environment.

Remediation Guide

M0814 Static Network Configuration

Unauthorized connections can be prevented by statically defining the hosts and ports used for automation protocol connections.

M0807 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.

M0930 Network Segmentation

Segment operational assets and their management devices based on their functional role within the process. Enabling more strict isolation to more critical control and operational information within the control environment.

M0810 Out-of-Band Communications Channel

Provide an alternative method for alarms to be reported in the event of a communication failure.

Detection

Detection of Alarm Suppression

Risk Assessment

Finding	Severity	Impact
Alarm Suppression technique applicable	Low	Inhibit Response Function

CWE Categories

CWE ID	Title
CWE-400	Uncontrolled Resource Consumption