Security teams can detect VBA Stomping by comparing the visible VBA source in a macro-enabled document with the compiled macro content stored inside it. A mismatch suggests the source was replaced while the compiled code remained malicious. Inspect suspicious Office files that run macros but show little or no readable VBA text.
How VBA Stomping Hides Malicious Macro Behaviour
vba stomping works because the macro document contains two views of the same code: the readable VBA source and the compiled macro stream that Office executes. An attacker can alter the visible source so inspection looks harmless while the compiled content still carries the malicious logic. That means the absence of obvious macro text does not prove a document is safe.
For defenders, the practical takeaway is that triage has to look at the document as a package, not just at the readable code window. Suspicious macro-enabled files can still trigger execution even when the source pane is sparse, blank, or misleading, so the visible text alone is an incomplete indicator.
What To Look For In Suspicious Office Documents
The strongest clue is a mismatch between what analysts can read and what the file is capable of doing. If a document prompts macro execution, behaves like a macro carrier, or shows signs of automation while the source code appears absent or stripped, treat that as a signal to inspect the embedded compiled macro content. The same logic applies when the document’s surface text looks intentionally cleaned up or minimally informative.
Inspection should focus on the file’s internal consistency. Compare the macro source with the compiled content stored inside the document, and treat unexplained differences as evidence of tampering. This is especially important in investigations where macro abuse is used to stage later payload delivery or to conceal the true behaviour of the document until it is opened in Office.
Malware Guide covers how malware families hide execution logic, including file-based evasion patterns such as compile-after-delivery and obfuscated payloads that are relevant when reviewing suspicious Office documents.
Why This Matters For Detection Workflows
VBA Stomping is a detection problem because it breaks a common assumption: that readable source reflects executable intent. If analysts rely only on source review, they can miss malicious code that survives inside the compiled stream. That creates a blind spot in email triage, sandboxing, and incident response workflows that score Office files by visible macro content alone.
Detection also needs to account for automation at scale. Large document sets, attachment detonation pipelines, and helpdesk or SOC triage queues can all miss the discrepancy if the inspection process is reduced to a quick text review. The value of the technique is not stealth through sophistication alone, but stealth through analyst assumption.
MITRE ATT&CK Enterprise Matrix is useful for mapping the downstream behaviours that often follow macro-based execution, while SANS Security Resources supports detection engineering practices for building better inspection and triage workflows.
Risk and Threat Considerations
VBA Stomping matters because it lets a malicious document present a benign face to reviewers while preserving executable behaviour inside the file. The result is a gap between analyst confidence and actual file content, which can delay containment and let the attachment progress further into the environment.
Failure mechanism: The attacker replaces the visible VBA source, but the compiled macro stream remains intact and executable, so source-based inspection misses the malicious logic.
Impact: Security teams may approve or down-rank a weaponised document, increasing the chance of macro execution, payload delivery, and follow-on compromise.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
MITRE ATT&CK addresses the attack and risk surface, while CIS Controls v8 and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| MITRE ATT&CK | T1204 — User Execution | Macro documents rely on user-opening behavior to trigger malicious code. |
| T1059 — Command and Scripting Interpreter | VBA macros are a scripting path often used to run malicious logic. | |
| Recommendation — Map suspicious Office attachments to user-execution paths and alert on macro-enabled delivery. Hunt for script-based execution chains inside Office documents and detonate suspicious files. | ||
| CIS Controls v8 | CIS-10 — Malware Defenses | Macro-stomped documents are malware delivery artifacts that need content inspection and detection. |
| CIS-13 — Network Monitoring and Defense | Macro-delivered payloads often generate follow-on network activity that defenders should monitor. | |
| Recommendation — Inspect Office documents for malicious embedded content before users can execute macros. Correlate suspicious document opens with downstream network and endpoint telemetry. | ||
| NIST CSF 2.0 | DE.CM-01 — Networks and network services are monitored to detect potential cybersecurity events | Macro stomping detection depends on monitoring suspicious file and execution activity. |
| DE.AE-03 — Potential adverse events are analyzed to better understand attack targets and methods | Analysts must interpret source/compiled mismatches as a potential adversary method. | |
| Recommendation — Monitor macro-enabled document activity and alert on anomalous execution patterns. Analyze mismatched macro source and compiled content as a likely adversary technique. | ||
Practitioner Guidance
What to verify: Do not trust a document just because the VBA editor shows little or no code. Verify the visible source against the compiled macro content and treat any mismatch as a tampering indicator worth escalation.
What to prioritise: Focus on macro-enabled attachments that arrive through email, collaboration tools, or downloads from untrusted sources, especially when the file’s behaviour suggests automation but the readable VBA looks empty or unusually thin.
Practitioner takeaway: The detection test is consistency, not visibility, if the code that runs and the code you can read do not match, assume the document deserves deeper analysis rather than a quick pass.
Related resources from NHI Mgmt Group
Deepen Your Knowledge
Free weekly newsletter
Subscribe to the NHI & AI Identity Journal
The latest on NHI and Agentic AI security – articles, research, breaches, news and events every week.
Bonus 33% off our NHI Course when you subscribe.
Reviewed and updated by the NHIMG editorial team on October 18, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org