Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 90e8d7eed259d810…

MALICIOUS

Office (OLE) / .XLSX

187.4 KB
MD5: a2e80e98b6693acf53212bd2c9c16583 SHA-1: 68ca52b1133e578c3e3c2af5810da5a3a4951a8c SHA-256: 90e8d7eed259d81086ca450a552794b61664ddd56de7a0bf13a13e94156ec18f
240 Risk Score

Malware Insights

Formbook · confidence 95%

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

The sample is an encrypted Office document, identified by ClamAV as Doc.Downloader.Formbook. Heuristics indicate it uses an Equation Editor OLE object, a common exploit carrier. The encryption and malformed structure suggest it's designed to bypass static analysis and deliver a malicious payload, consistent with Formbook's typical behavior.

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.