Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 c0945280218aa1fd…

MALICIOUS

Office (OLE) / .XLSX

441.5 KB
MD5: 44e50536f1d63ee7db4228446f5ae99f SHA-1: c40de858890f7297e50b0b2dd0644dbb482b7055 SHA-256: c0945280218aa1fd2ed370b1331f7393d2b2313e27be7bfd523017dd324a10be
240 Risk Score

Malware Insights

Formbook · confidence 95%

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

The file is a password-encrypted Excel spreadsheet, a common delivery mechanism for macro-based malware. Heuristics indicate the presence of an embedded OLE object exploiting Equation Editor, which is a known technique for delivering malware. ClamAV detection explicitly identifies the file as Doc.Downloader.Formbook, confirming its malicious nature and family. The embedded OLE object is the primary vector for executing the malicious payload.

Heuristics 6

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Default-encrypted OOXML 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.
  • Encrypted Office package with CFB FAT corruption critical OLE_ENCRYPTED_AND_MALFORMED
    Encrypted-package shape co-occurs with FAT-chain corruption — the documented combined evasion form.
  • ClamAV: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0
  • Default-encrypted OOXML exploit carrier layout high OOXML_ENCRYPTED_EXPLOIT_CARRIER_SHAPE
    Default-password encrypted OOXML package contains embedded OLE object parts and additional activation/decoy parts. This layout is common in malicious Excel exploit delivery and requires inspecting the decrypted package.
  • Office document is password-encrypted medium OFFICE_ENCRYPTED_PACKAGE
    OLE container holds MS-OFFCRYPTO encrypted package (Standard Encryption (Office 2007, AES)).
  • Office OOXML encrypted with default VelvetSweatshop password medium OFFICE_DEFAULT_PASSWORD_ENCRYPTED_OOXML
    OLE EncryptedPackage decrypts with Excel's built-in VelvetSweatshop password. Office opens this transparently, and malware uses it to hide OOXML exploit parts from scanners that only inspect the outer OLE container.

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