Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 cf428aa93ac3f8f5…

MALICIOUS

Office (OOXML) / .XLSX

179.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2022-03-15
MD5: f6036e802bb253a20c30600f01e0efaa SHA-1: 1b752966d5c2be64ee2b2a329d6f4be263307d88 SHA-256: cf428aa93ac3f8f596abece089fd497bce404e1542efae6298339392e4d8f9fb
168 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204 Malicious File Execution T1059 Command and Scripting Interpreter

The critical ClamAV detection and high-severity heuristics for OLE Equation Editor exploitation (CVE-2018-0798) strongly indicate this XLSX file is a malicious downloader. The embedded OLE object, specifically the Equation Editor component, is a known vector for delivering malware. The ClamAV signature 'Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0' directly attributes the file to the Formbook family, which is known for its downloader capabilities.

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
36a1df95e182cd9b42aa41a4ffe381ea4df24aae5bb350d5dc2b4aa491ba6e48		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 4096 bytes
ooxml_oleobject_00_ole10native_00.bin
b471e141846df8f6e52fab9528cc4e9bc72d12bf46b24c48e1d9dfcb94c9c108		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: Ole10nAtivE 1597 bytes
emf_00.emf
bc1a75f99b79c98350da4bb5561eac01186dacf8d64f3ae8d4822e1a028644d9		 ooxml-emf OOXML EMF part: xl/media/image7.emf 1099960 bytes

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