Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 45bf39b77ce8b035…

MALICIOUS

Office (OOXML) / .XLSX

408.1 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000
MD5: 098208b00c17484d174d1a85811a8b73 SHA-1: 10999ae1620530f9c979bcb35cb81120800a8e4f SHA-256: 45bf39b77ce8b035e919790c631a7a02ab9f39b084eba8bb655d4c75a4deb7a8
168 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204 Malicious Link T1059 Command and Scripting Interpreter

The critical ClamAV detection identifies this file as Formbook, a known downloader. Heuristics indicate the presence of an embedded Equation Editor OLE object, specifically triggering CVE-2018-0798, which is a common vector for delivering malware. The embedded OLE object likely contains code to download and execute a second-stage 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
4853971e53c73ce83b44445a502c1d05753badf0d7f4ccbb50989627bbcc8f88		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 3584 bytes
ooxml_oleobject_00_ole10native_00.bin
4db235fbfc146d04c1b74e67cff4f5a518157d886f4a5d82ea39fa7313322b56		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: Ole10naTivE 1347 bytes
emf_00.emf
b7ac322616221bdf432e7d907e9a487a62a568faa7d2410c60d8416873e62793		 ooxml-emf OOXML EMF part: xl/media/image6.emf 1099960 bytes

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