Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 ce8ca35bad6b0e2c…

MALICIOUS

Office (OOXML) / .XLSX

1.11 MB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000
MD5: f423597222898a097d30adbc3d168a87 SHA-1: e199e53576397ee7296e3b0f5ad3cee1ca147e06 SHA-256: ce8ca35bad6b0e2c5aeefed0b34b09dff56fdce32d14246c011d9401bc6e3ba2
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 and high-severity heuristics for an embedded Equation Editor OLE object with an anomalous Ole10Native stream strongly indicate a downloader. The presence of a hidden worksheet further supports the concealment of malicious content. The file is identified as Formbook, a known information-stealing malware family, which often uses this delivery method.

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.
  • ClamAV: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0
  • Equation Editor object carries payload-like Ole10Native stream high OLE_EQUATION_OLE10NATIVE_PAYLOAD_ANOMALY
    Embedded OLE object declares the Equation Editor CLSID but stores a large high-entropy Ole10Native stream with malformed package sizing. This is an exploit-shaped Equation/OLE payload container seen in malicious OOXML samples. It is not assigned to a specific CVE unless the MTEF/Equation Native primitive also matches.
  • 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
e159428d25348d0accdf0f15064e90bc7ede07e578e44bc51e8bb246f0de40a1		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 1035264 bytes
ooxml_oleobject_00_ole10native_00.bin
7997677c0c9901d5d4fcd4b1feb937ac44cd56f4282417cde629c3408636e604		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: Ole10naTIvE 1024982 bytes
emf_00.emf
6f07e396ea596bad1c10a91f30e8eecf3dbcc7fc26a53b8d5f3cd61434e1b1c0		 ooxml-emf OOXML EMF part: xl/media/image7.emf 1099960 bytes

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