Office (OOXML) / .DOCX malware analysis — malicious · 0aadc47fb5644a46

MALICIOUS

Office (OOXML) / .DOCX

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

MD5: 0b25f074b1a7ee7e3a553bdaeb43d11b SHA-1: d2e242724e6674de5c8a601134285031503c01c5 SHA-256: 0aadc47fb5644a461486c1c46ac4139f7db57df540dbc80faa0a1501bedff956

224 Risk Score

Malware Insights

MITRE ATT&CK

T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

The OOXML document contains an altChunk that imports an RTF object. This RTF object is configured to automatically link to and update an external OLE object, indicated by the RTF_OBJAUTLINK and RTF_OBJUPDATE heuristics. The external relationship points to a remote template, https://my.dexserver.com/assets/css/dotms_4/TqIWUfvvJYlNB.dotm, which is likely a malicious payload or a further stage of infection. The exploitation of OLE objects and remote templates suggests an attempt to execute arbitrary code.

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/TqIWUfvvJYlNB.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/TqIWUfvvJYlNB.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/TqIWUfvvJYlNB.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` `6db290dd0671b9ede20dd8e0eaa3919f5c29ff49452f0a7eeefcb76099adb829`	rtf-objdata-decoded	RTF \objdata at offset 0x78F1	75851 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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