Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 e87e6ec257de9639…

MALICIOUS

Office (OOXML) / .XLSX

180.9 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2022-02-21
MD5: fcc292fb7d7c1cfa8819109ad9da4190 SHA-1: d962cbc7ab31924f81b25926375237b1ed73796a SHA-256: e87e6ec257de9639cdea4c05ad1e6539081842fcc5fadaa00da6b098b3af5bff
168 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204.002 Malicious File

The critical ClamAV detection identifies this file as Doc.Downloader.Formbook, a known downloader family. High-severity heuristics indicate the presence of an embedded Equation Editor OLE object, specifically triggering CVE-2018-0798. This suggests the file is designed to exploit this vulnerability to download and execute a secondary payload, consistent with Formbook's typical behavior.

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
8a136f45f81f8ac7b7a76647b35e255af65f1cc9ee43529d166684d8685bc764		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 4096 bytes
ooxml_oleobject_00_ole10native_00.bin
e5bef5db0d68fdf9d65b0422bf75179a65a096d9bda091fb704168a52a7900af		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: OLE10natIve 1616 bytes
emf_00.emf
44c4a886ed60b51c61a987c08e31f589fc238d469ece56a9e9df94df99d8d03a		 ooxml-emf OOXML EMF part: xl/media/image7.emf 1099960 bytes

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