cyberstrikeus T0803 Block Command Message
High-Level Description
Adversaries may block a command message from reaching its intended target to prevent command execution. In OT networks, command messages are sent to provide instructions to control system devices. A blocked command message can inhibit response functions from correcting a disruption or unsafe condition.
Kill Chain Phase
- Inhibit Response Function (TA0107)
Platforms: ICS
What to Check
- Identify if Block Command Message technique is applicable to target ICS environment
- Check ICS/SCADA systems for indicators of Block Command Message
- Verify mitigations are bypassed or absent (3 known mitigations)
- Assess detection coverage (1 detection strategies)
How to Test
Identify Attack Surface
Determine if the target ICS/SCADA environment is susceptible to Block Command Message by examining operational technology systems and network architecture.
Assess Existing Defenses
Review whether mitigations for T0803 are in place. If defenses are absent or misconfigured, this technique may be exploitable in the ICS environment.
Remediation Guide
M0810 Out-of-Band Communications Channel
Provide an alternative method for sending critical commands message to outstations, this could include using radio/cell communication to send messages to a field technician that physically performs the control function.
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.
M0814 Static Network Configuration
Unauthorized connections can be prevented by statically defining the hosts and ports used for automation protocol connections.
Detection
Detection of Block Command Message
Risk Assessment
| Finding | Severity | Impact |
|---|---|---|
| Block Command Message technique applicable | Low | Inhibit Response Function |
CWE Categories
| CWE ID | Title |
|---|---|
| CWE-400 | Uncontrolled Resource Consumption |