Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 a4b4a0b19ab4e039…

MALICIOUS

Office (OOXML) / .XLSX

176.2 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000
MD5: 2e99bf41a05731ab85b55f73130a327e SHA-1: 35a70f83616bda0280176f60dffe05eb92f11cfb SHA-256: a4b4a0b19ab4e03991a69ce6fbeecaa8e4c19100a9d1924a51b8eb19788468a1
168 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204 Malicious Link T1204.002 Malicious File T1059 Command and Scripting Interpreter

The critical ClamAV detection of 'Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0' strongly suggests the Formbook family. The presence of an embedded Equation Editor OLE object, coupled with the CVE-2018-0798 anomaly, indicates exploitation of a vulnerability within the Equation Editor to facilitate the download and execution of a malicious payload. The hidden worksheet is likely used to conceal malicious content.

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
e002578c041667597bd1d2516482a843947a3bbd4f6fc61f5cdccc7c85a85c4b		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 4096 bytes
ooxml_oleobject_00_ole10native_00.bin
39e64a09fafeed8b3d95b23832ce598d3e5453f107fc7e09a44dbdc481a29f56		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: olE10nAtIVe 1657 bytes
emf_00.emf
65da96b92c9dee12c64aa27d0f86154c275d290cd2a08b1f2fcf98215fab6031		 ooxml-emf OOXML EMF part: xl/media/image6.emf 1099960 bytes

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