Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 f40be1bf04a363bc…

MALICIOUS

Office (OLE) / .XLSX

187.7 KB First seen: 2022-04-06
MD5: 058564a9dd0aed80c10c3347c04f97ef SHA-1: b429fbcaa8b225c6485150f3f7b9fe19ae874ea6 SHA-256: f40be1bf04a363bcce123f26dbbb1aa211116eab6c1e76e0fcf6ce9297c442c0
240 Risk Score

Malware Insights

Formbook · confidence 95%

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

The sample is a password-encrypted Office document, identified as a likely exploit carrier due to its structure and the presence of an Equation Editor OLE object. ClamAV detection explicitly names this as Doc.Downloader.Formbook, indicating its function as a downloader for the Formbook malware family. The encryption and embedded OLE object are consistent with techniques used to bypass static analysis and deliver malicious content.

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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