Win.Trojan.Cap-1 — Office (OLE) malware analysis

Static analysis result for SHA-256 5181f4f42f46369e…

MALICIOUS

Office (OLE)

30.5 KB Created: 1997-09-17 15:22:00 Authoring application: Microsoft Word 6.0 First seen: 2019-06-27
MD5: e0660a836dcf6ed924aa8dfb6d84ac92 SHA-1: 8a1551a662e37cfe9e4470a9606f86b99b4bc8bc SHA-256: 5181f4f42f46369eb55eede2b70655957d63e4a0e94b338f4db72976db3e0617
220 Risk Score

Malware Insights

Win.Trojan.Cap-1 · confidence 95%

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

The file is identified as a malicious OLE document containing legacy WordBasic macro virus markers and suspicious OLE structure anomalies. ClamAV specifically detects it as Win.Trojan.Cap-1. The embedded OLE object, likely containing a malicious payload, is the primary indicator of compromise.

Heuristics 5

  • ClamAV: Win.Trojan.Cap-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Trojan.Cap-1
  • Embedded Office document has suspicious static findings critical EMBEDDED_OFFICE_CHILD_STATIC_TRIAGE
    A CFB/OLE Office document was found inside another file type and its carved contents matched Office exploit or payload heuristics. This catches wrapped exploit documents where the top-level file routes to a PE, archive, or generic scanner instead of Office.
  • Legacy WordBasic macro-virus markers high OLE_LEGACY_WORDBASIC_MACRO_VIRUS
    OLE Word document contains legacy WordBasic auto-execution macro markers such as AutoOpen plus ToolsMacro/MacroFile/fileMacro/globMacro or named historical macro-virus strings. These old Word 6/95 macro forms are not exposed as a modern VBA project, so normal VBA source extraction can miss them.
  • OLE document has large unaccounted-for region high OLE_SLACK_ANOMALY
    OLE file is 31,232 bytes but its declared streams total only 12,750 bytes — 18,482 bytes (59%) live in unallocated sector slack. This is the canonical hiding place for pre-macro-era Office exploit payloads (XOR-encoded shellcode reached via a parser pointer-corruption bug in the document structure).
  • CFB header with no readable streams medium OLE_PARSE_EMPTY_STREAMS
    This finding applies to a carved embedded Office document found at a nonzero offset inside the submitted file, not directly to the top-level document. The file begins with a valid OLE2/CFB header but exposes no directory streams. A non-empty compound document with an unreadable directory is anomalous — it is seen with truncated/corrupt files and, more importantly, with content deliberately shifted off byte boundaries to defeat parsers while the host application still recovers the object.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
embedded_office_off00001a40.ole embedded-office Embedded OLE/CFB Office body inside ole container at offset 0x1A40 24512 bytes
SHA-256: 11da2ae930e7d30d8c81137d2ab4359fd0daad1521a6cf0074d8be7984cab431

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