Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 7f7a9411623a69a1…

MALICIOUS

Office (OOXML) / .XLSX

179.6 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2022-03-16
MD5: 15c3fdf17922367be22a7dcd60898823 SHA-1: 541eed50009ef2169b03206b626768af450ce09c SHA-256: 7f7a9411623a69a1392031f34ce9fe1608db6b14d660cd58899ee5eba78979ff
168 Risk Score

Malware Insights

Formbook · confidence 95%

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

The sample is an Excel file containing an embedded OLE object, specifically an Equation Editor object. Heuristics indicate this object exploits CVE-2018-0798, a known vulnerability in Equation Editor. ClamAV detection confirms this is a Formbook downloader. The embedded OLE object likely serves 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
905ab2ab62a3035caf4b9381a572466f206f7cbf8259553f19ac70a760257196		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 4096 bytes
ooxml_oleobject_00_ole10native_00.bin
8791d7441f88ba4037f2b45f506ffadf9989015828976deae0b04ace4c98bbbd		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: oLE10nAtive 1681 bytes
emf_00.emf
bc1a75f99b79c98350da4bb5561eac01186dacf8d64f3ae8d4822e1a028644d9		 ooxml-emf OOXML EMF part: xl/media/image7.emf 1099960 bytes

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