Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 d1bf2fbffa905d29…

MALICIOUS

Office (OOXML) / .XLSX

180.8 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000
MD5: a8e633f10004b0cd07aa107c41abb67e SHA-1: 73ce1c5b6c82f1924a9fe37585cc255818ef9ed6 SHA-256: d1bf2fbffa905d29d876be427445e9c007ced0fa89d75bc27d58a0411701144f
168 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204.002 Malicious File

The critical ClamAV detection identifies this file as Formbook, a known downloader. The presence of an embedded Equation Editor OLE object, coupled with heuristics indicating an anomalous native stream and invalid MTEF version, strongly suggests exploitation of CVE-2018-0798. This vulnerability is commonly used to download and execute a second-stage payload, consistent with Formbook's typical behavior. No scripts were extracted, but the OLE object itself is the primary attack vector.

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
234e79e3418d734a2a24c30028506e1145c9daf3f5744da838879b66e0ffcb03		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 4096 bytes
ooxml_oleobject_00_ole10native_00.bin
44ad45df8d5702643416ac2bd36c3393b269f500047dc43ec0c38210e34b89f1		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: OLE10NATIvE 1681 bytes
emf_00.emf
29ab6e7557a5435fafd4e6867df7356d561d984dfd5aaeadc96c5924fd6fc507		 ooxml-emf OOXML EMF part: xl/media/image7.emf 1099960 bytes

Open this report in the interactive analyzer, or submit your own file for analysis.