Executive Summary
Pre-OS Boot (T1542) is a MITRE ATT&CK technique associated with Stealth, Persistence. Adversaries may abuse Pre-OS Boot mechanisms as a way to establish persistence on a system.
Why Attackers Use It
Attackers use Pre-OS Boot because it provides a reliable way to advance their objective within the Stealth, Persistence tactic, often with a favorable balance of impact versus detectability on 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 abuse Pre-OS Boot mechanisms as a way to establish persistence on a system. During the booting process of a computer, firmware and various startup services are loaded before the operating system. These programs control flow of execution before the operating system takes control.(Citation: Wikipedia Booting)
Adversaries may overwrite data in boot drivers or firmware such as BIOS (Basic Input/Output System) and The Unified Extensible Firmware Interface (UEFI) to persist on systems at a layer below the operating system. This can be particularly difficult to detect as malware at this level will not be detected by host software-based defenses.
Attack Flow
- Attacker gains the prerequisite access or context described below.
- Attacker executes Pre-OS Boot to achieve its tactical objective (Stealth, Persistence).
- Resulting access/data/effect is leveraged to advance the broader attack chain (see Related Techniques).
Prerequisites
- Platform(s): 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 Pre-OS Boot. 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
| Event ID | Log Channel | What It Indicates |
|---|
| Environment-specific | Relevant Windows channel(s) | Correlate authentication, process, object-access, and configuration events with the observed execution context. |
Sysmon Events
| Sysmon Event ID | Name | Why It's Relevant Here |
|---|
| Environment-specific | Validate configured telemetry | Use process, network, file, registry, DNS, or image-load telemetry only when relevant and enabled. |
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
- Confirm that the observed behavior is consistent with Pre-OS Boot and rule out expected administrative or application activity.
- Establish the first-seen time, initiating identity, source system, target system, and affected resources.
- Collect relevant host, identity, network, cloud, and application telemetry for the surrounding time window.
- Correlate parent and child activity, remote connections, file or configuration changes, and related ATT&CK techniques.
- Determine scope by searching for the same observable across peer assets and identities.
- Preserve volatile evidence and record confidence, assumptions, and telemetry gaps before containment.
Containment
- Isolate affected host(s)/account(s) identified during investigation.
- Revoke or rotate any credentials/tokens potentially exposed.
- Apply the mitigations listed below where not already enforced.
- Validate no related techniques (see Related Techniques) were chained against the same asset.
Mitigation
- M1035 -- Limit Access to Resource Over Network: Restrict access to network resources, such as file shares, remote systems, and services, to only those users, accounts, or systems with a legitimate business requirement.
- M1047 -- Audit: Auditing is the process of recording activity and systematically reviewing and analyzing the activity and system configurations.
- M1051 -- Update Software: Software updates ensure systems are protected against known vulnerabilities by applying patches and upgrades provided by vendors.
- M1026 -- Privileged Account Management: Privileged Account Management focuses on implementing policies, controls, and tools to securely manage privileged accounts (e.g., SYSTEM, root, or administrative accounts).
- M1046 -- Boot Integrity: Boot Integrity ensures that a system starts securely by verifying the integrity of its boot process, operating system, and associated components.
Related Techniques
- T1542.001
- T1542.002
- T1542.003
- T1542.004
- T1542.005