Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 d86c329890b3d00d…

MALICIOUS

Office (OOXML) / .XLSX

179.9 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2022-03-07
MD5: b97095bec9e52bb6463f881c7eefc2f2 SHA-1: 22b1135189599871821c864e19f8e679a2fd4012 SHA-256: d86c329890b3d00d32828f203ce8b6db2e75c561745102bf4252cd0b976feb35
168 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204 Malicious Link T1204.001 Malicious Link: Malicious Link T1059 Command and Scripting Interpreter T1071 Application Layer Protocol

The file contains an embedded OLE object, specifically identified as an Equation Editor object, which triggers heuristics for CVE-2018-0798. This indicates the file is designed to exploit a vulnerability within the Equation Editor component. The ClamAV detection explicitly names 'Doc.Downloader.Formbook', strongly suggesting the Formbook family and a downloader functionality. The presence of hidden sheets further supports the concealment of malicious components.

Heuristics 5

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/oleObject1.bin contains the Equation Editor CLSID, the legacy component exploited by CVE-2017-11882, CVE-2018-0802, and CVE-2018-0798.
  • CVE-2018-0798 — anomalous Equation Editor native stream high CVE likely CVE_2018_0798_EQUATION_NATIVE_ANOMALY
    Embedded Equation Editor OLE data contains anomalous native stream bytes consistent with a CVE-2018-0798-style Equation Editor exploit. This is treated as likely CVE evidence because the Equation object is malformed and payload-like, but it does not match the exact public matrix-overflow byte signature.
  • ClamAV: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0
  • Embedded OLE object medium OOXML_OLE_OBJECT
    Document contains an embedded OLE object
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 1 hidden sheet(s) — hidden sheets are commonly used to conceal macro code, staging data, or intermediate payload construction

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
ooxml_oleobject_00.bin
a28b9e4d022e584cb2fc5b82ab40bd49eb7b3f22a1b5c6d3085157164afcd50f		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 4608 bytes
ooxml_oleobject_00_ole10native_00.bin
8c923c118498f66218e9f14165c65d3897f1baa846963ae7e8acd832b8c381cc		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: olE10NaTIVe 2098 bytes
emf_00.emf
bc1a75f99b79c98350da4bb5561eac01186dacf8d64f3ae8d4822e1a028644d9		 ooxml-emf OOXML EMF part: xl/media/image7.emf 1099960 bytes

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