Office (OOXML) / .DOCX malware analysis — malicious · 116f0f9b74f5a9b4

MALICIOUS

Office (OOXML) / .DOCX

475.7 KB Created: 2021-08-04 12:45:00 UTC Authoring application: Microsoft Office Word 12.0000

MD5: 0aaa6f0186a7804c407c268651ddf512 SHA-1: 4df2e1f3b765ba4d73dd514a286079c7b78a4f04 SHA-256: 116f0f9b74f5a9b47bf1e1023249c678e2931e7b5d3dd14a56e6bb2fa6676b00

224 Risk Score

Malware Insights

MITRE ATT&CK

T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

The OOXML document utilizes an altChunk to import an RTF object, which in turn contains OLE object data. Heuristics indicate that this OLE object is automatically linked and its update is forced, suggesting an attempt to exploit OLE vulnerabilities for execution. Furthermore, a remote template URL is referenced, indicating the document is designed to download and execute a secondary payload. The presence of OLE object data and remote template injection strongly suggests a malicious intent to compromise the user's system.

Heuristics 8

altChunk imports embedded RTF (RTF injection) critical OOXML_ALTCHUNK_RTF

Document inlines an embedded RTF via an aFChunk relationship and a <w:altChunk> body element. This is the canonical RTF-injection wrapper used to smuggle RTF exploits (Equation Editor / URL Moniker / objdata) past DOCX-only scanners. Word opens the wrapper and executes the RTF inline. Recursing into the RTF for the exact exploit primitive.
Automatically linked OLE object high RTF_OBJAUTLINK

(in altChunk RTF word/altChunk1.rtf) RTF contains \objautlink — an automatically linked OLE object surface that can be updated or activated when Word opens the document.
\objupdate forces OLE activation high RTF_OBJUPDATE

(in altChunk RTF word/altChunk1.rtf) RTF contains \objupdate — forces automatic OLE object instantiation when the document is opened, bypassing user interaction. Almost exclusively seen in Equation Editor exploit documents.
Remote template injection high OOXML_REMOTE_TEMPLATE

Document references a remote template URL (https://my.dexserver.com/assets/css/dotms_4/DAGmBIAgSSFyyTc.dotm) — a common remote-template-injection vector used by Hancitor, Emotet and many phishing campaigns. Word can fetch and apply the remote template; macros in that template may execute depending on Office policy and trust state.
OLE object data medium RTF_OBJDATA

(in altChunk RTF word/altChunk1.rtf) RTF contains 1 \objdata section(s) — embedded OLE objects
External relationship medium OOXML_EXTERNAL_REL

External target in word/_rels/settings.xml.rels: https://my.dexserver.com/assets/css/dotms_4/DAGmBIAgSSFyyTc.dotm
Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
Embedded URL info EMBEDDED_URL

One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
URL https://my.dexserver.com/assets/css/dotms_4/DAGmBIAgSSFyyTc.dotm
- http://schemas.openxmlformats.org/markup-compatibility/2006
- http://schemas.openxmlformats.org/officeDocument/2006/relationships
- http://schemas.openxmlformats.org/officeDocument/2006/math
- http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing
- http://schemas.openxmlformats.org/wordprocessingml/2006/main
- http://schemas.microsoft.com/office/word/2006/wordml

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`objdata_00_off000078f1.bin` `4dcc9abf258e5db8fc4ada4be63ac0393bf2460aa6a3df9eadab668ab130346c`	rtf-objdata-decoded	RTF \objdata at offset 0x78F1	75406 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.79, consistent with packed or encrypted content.

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