Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 dd2cf4b14071f3c2…

MALICIOUS

Office (OOXML) / .XLSX

180.7 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000
MD5: a0dd0991199ef44927ccc930a13abef2 SHA-1: 01fa614d77afacbbc4a48942e48bae3dbcf09288 SHA-256: dd2cf4b14071f3c2df8100a638ebb8e381cf217bdb9398c183027037222490bf
168 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204.002 Malicious File T1566.001 Spearphishing Attachment

The critical ClamAV detection and high-severity heuristics for OLE Equation Editor anomalies (CVE-2018-0798) strongly indicate exploitation of a vulnerability within the Equation Editor component. This is a common delivery mechanism for malware like Formbook, which often acts as a downloader. The presence of embedded OLE objects and a hidden worksheet further supports this. The ClamAV signature specifically names 'Formbook', increasing confidence in the family attribution.

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
d90b8566958ce04ffb5745a303f7574ccf8e8f6bf8872fc59d01e3cc241d48cd		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 4096 bytes
ooxml_oleobject_00_ole10native_00.bin
5a21e007637036f20f9fe9261bbf6c55493bda8364eead4d3da8bb16f78d11da		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: olE10nAtIvE 1526 bytes
emf_00.emf
332d3e2efa76243912ff09696372700ca8ed833a5c0fef8d90dfc136190ebb78		 ooxml-emf OOXML EMF part: xl/media/image7.emf 1099960 bytes

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