Formbook — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 904ad8c7965b4ea9…

MALICIOUS

Office (OOXML) / .XLSX

179.6 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2022-03-03
MD5: 9a0f94e1a6186749dc5969688a077446 SHA-1: 6748ea6955613fd43c5ce2f94232274886f89457 SHA-256: 904ad8c7965b4ea993011c9346ff4b6e3f45ee09e5f09297c35843aba5b4edec
168 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204.002 Malicious File T1566.001 Spearphishing Attachment

The file is identified as malicious by ClamAV with the signature Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0. Static analysis revealed an embedded Equation Editor OLE object with anomalies indicative of CVE-2018-0798. This vulnerability is often exploited to download and execute further malicious payloads. The presence of a hidden worksheet further suggests an attempt to conceal malicious activity.

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
f2567e4040bbfb4ef85aee13b1f3ab896361032298683f134d20852d05a71ca9		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject1.bin 4096 bytes
ooxml_oleobject_00_ole10native_00.bin
4ecc4fe8d9a2aea0885935e409e8f9d108cef8eb55e4f6b47d5c7be1f8b5bd6c		 ole-package OOXML xl/embeddings/oleObject1.bin Ole10Native stream: oLE10naTIVe 1675 bytes
emf_00.emf
bc1a75f99b79c98350da4bb5561eac01186dacf8d64f3ae8d4822e1a028644d9		 ooxml-emf OOXML EMF part: xl/media/image7.emf 1099960 bytes

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