Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 59ae0b8bb8ac357d…

MALICIOUS

Office (OLE) / .XLSX

185.6 KB First seen: 2022-04-04
MD5: 1fde2c48b145e2caba9af4fa338633f9 SHA-1: 72b80017a0acce39bf8f41cf9aa5a3c482ee2989 SHA-256: 59ae0b8bb8ac357d783c99bdab577799bd65bf354f5b517e0c70bdb9252a6f34
160 Risk Score

Malware Insights

Formbook · confidence 95%

The file is identified as a malicious Office document by ClamAV, specifically as 'Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0'. It is password-encrypted and exhibits OLE FAT corruption, indicating a deliberate attempt to obscure its contents. The detection name suggests it functions as a downloader, likely for the Formbook malware family, and the presence of encrypted OOXML points towards VBA macro usage for execution.

Heuristics 4

  • 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
  • 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.