Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 809c4e76bdc67512…

MALICIOUS

Office (OOXML) / .XLSX

180.0 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2022-03-09
MD5: 8be3ee43f55f9e01cf17816d34679499 SHA-1: 5f9f41ea5195443fe02429855e3eff8b6a9caafe SHA-256: 809c4e76bdc6751247fc1f961240c1696ed7456aa9a6902e6b0fd76345ee5a9a
168 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204 Malicious File T1204.002 Malicious File: User Execution: Malicious Attachment T1059 Command and Scripting Interpreter

The critical ClamAV detection identifies this file as Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0, indicating it's a Formbook downloader. High-severity heuristics confirm the presence of an embedded Equation Editor OLE object, specifically triggering CVE-2018-0798, which is a known vulnerability used to deliver malware. The embedded OLE object likely contains the exploit code to download and execute a secondary payload.

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
de3978f368d043492dc2efeeef8a06b5f64bdedef6ede1ee587642e407a5ffd3		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 3584 bytes
ooxml_oleobject_00_ole10native_00.bin
5399617b1e91ce6dea3fe8efc4fd4168985658c96c33a2d7468dbd15bb7ab2ce		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: Ole10nativE 1432 bytes
emf_00.emf
bc1a75f99b79c98350da4bb5561eac01186dacf8d64f3ae8d4822e1a028644d9		 ooxml-emf OOXML EMF part: xl/media/image7.emf 1099960 bytes

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