Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 eca1784247861d51…

MALICIOUS

Office (OOXML) / .XLSX

436.7 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000
MD5: 6a7d68de0b2d63cd53504e3abbf46996 SHA-1: 3bff34521fa2fe85a5fd8f1000bcd5db275bb199 SHA-256: eca1784247861d517c8d7626ef78669dcd1dc20e46fde840a45c7d26dae46886
168 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204 Malicious Link T1566.001 Spearphishing Attachment T1204.001 Malicious Link

The critical ClamAV detection identifies the file as 'Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0', strongly suggesting the Formbook family. High-severity heuristics indicate the presence of an embedded OLE object, specifically an Equation Editor object, which is anomalous and indicative of CVE-2018-0798. This exploit likely facilitates the download and execution of 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
c4668fabac0f39ec0803b2fa86b1e3520069c9b05ed0ffc90ee245bb31c54ba8		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 4096 bytes
ooxml_oleobject_00_ole10native_00.bin
cde840e92d50ffb66bbfc3b9a474e864415228c6b2c1b149933e1281b2eaa5fd		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: OLe10nATiVE 1912 bytes
emf_00.emf
8b4c2761abea7fcfae5aec04e874b3176128b5c52010d6d2badd202a38b321e7		 ooxml-emf OOXML EMF part: xl/media/image7.emf 1112336 bytes

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