Disable or Modify System Firewall

Executive Summary

Disable or Modify System Firewall (T1686) is a MITRE ATT&CK technique associated with Defense Impairment. Adversaries may disable or modify host-based or network firewalls to impair defensive mechanisms and enable further action.

Why Attackers Use It

Attackers use Disable or Modify System Firewall because it provides a reliable way to advance their objective within the Defense Impairment tactic, often with a favorable balance of impact versus detectability on ESXi, Linux, macOS, Network Devices, Windows environments. Defenders should assess this behavior in the context of the affected platform and adjacent activity rather than treating it as a standalone indicator.

MITRE Description

Adversaries may disable or modify host-based or network firewalls to impair defensive mechanisms and enable further action. Once an adversary has gathered sufficient privileges, they can tamper with firewall services, policies, or rule sets to remove restrictions on inbound or outbound traffic. For example, this may include turning off firewall profiles, altering existing rules to permit previously blocked ports or protocols, or adding new rules that create covert communication paths (e.g., adding a new firewall rule for a well-known protocol (such as RDP) using a non-traditional and potentially less securitized port.(Citation: change_rdp_port_conti)

Adversaries may disable or modify firewalls using different behaviors, depending on the platform. For example, in ESXi, firewall rules may be modified directly via the esxcli (e.g., via esxcli network firewall set) or via the vCenter user interface.(Citation: Broadcom ESXi Firewall)(Citation: Trellix Rnasomhouse 2024)

Attack Flow

1. Attacker gains the prerequisite access or context described below.
2. Attacker executes Disable or Modify System Firewall to achieve its tactical objective (Defense Impairment).
3. Resulting access/data/effect is leveraged to advance the broader attack chain (see Related Techniques).

Prerequisites

• Platform(s): ESXi, Linux, macOS, Network Devices, Windows
• ATT&CK does not define one universal permission requirement for this technique. Establish the required access from the observed implementation and affected platform.

Common Tools

• Tool attribution is implementation-specific. Use ATT&CK procedure examples and local telemetry to identify the binaries, services, scripts, accounts, or cloud resources involved.

Commands

No universal command represents Disable or Modify System Firewall. Capture the exact command line, arguments, parent process, account, host, and execution time from the investigated environment; do not operationalize unverified examples.

Network Traffic

• Network observability is implementation-dependent. Review DNS, proxy, firewall, flow, authentication, and packet telemetry around the activity window, then correlate remote endpoints and protocol behavior with host evidence.

Windows Events

Sysmon Events

Detection Opportunities

No MITRE detection guidance published for this technique.

Relevant ATT&CK Data Sources: N/A

Sigma Rules

A universal Sigma rule would create unreliable results because this technique has no single guaranteed observable. Build detection logic from a documented behavior and supported data source, scope it to the affected platform, and validate it against benign administrative activity before deployment.

Splunk Queries

Start with the data sources named in the detection section. Scope searches by asset, identity, and time window; correlate the primary behavior with preceding access and subsequent actions. A portable query is intentionally not provided where the technique lacks a universal schema or observable.

Investigation Workflow

1. Confirm that the observed behavior is consistent with Disable or Modify System Firewall and rule out expected administrative or application activity.
2. Establish the first-seen time, initiating identity, source system, target system, and affected resources.
3. Collect relevant host, identity, network, cloud, and application telemetry for the surrounding time window.
4. Correlate parent and child activity, remote connections, file or configuration changes, and related ATT&CK techniques.
5. Determine scope by searching for the same observable across peer assets and identities.
6. Preserve volatile evidence and record confidence, assumptions, and telemetry gaps before containment.

Containment

1. Isolate affected host(s)/account(s) identified during investigation.
2. Revoke or rotate any credentials/tokens potentially exposed.
3. Apply the mitigations listed below where not already enforced.
4. Validate no related techniques (see Related Techniques) were chained against the same asset.

Mitigation

• M1047 -- Audit: Auditing is the process of recording activity and systematically reviewing and analyzing the activity and system configurations.
• M1024 -- Restrict Registry Permissions: Restricting registry permissions involves configuring access control settings for sensitive registry keys and hives to ensure that only authorized users or processes can make modifications.
• M1022 -- Restrict File and Directory Permissions: Restricting file and directory permissions involves setting access controls at the file system level to limit which users, groups, or processes can read, write, or execute files.
• M1018 -- User Account Management: User Account Management involves implementing and enforcing policies for the lifecycle of user accounts, including creation, modification, and deactivation.

Related Techniques

• T1036.005
• T1047
• T1057
• T1059.003
• T1070.004
• T1082
• T1083
• T1105
• T1686.001
• T1686.002
• T1686.003