Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 acc4be02b6d34572…

MALICIOUS

Office (OLE) / .XLSX

187.0 KB
MD5: 69795e78fb23e13a62ebc183ef90b3ed SHA-1: e16a17d9001daf722aab876d3dab010218af2a23 SHA-256: acc4be02b6d345725689351b0de0b19ea35f356a60df8cf92318fe9ff96e474f
240 Risk Score

Malware Insights

Formbook · confidence 90%

MITRE ATT&CK
T1204.002 User Execution: Malicious File T1059 Command and Scripting Interpreter T1203 Exploit for Client Execution

The sample is a password-encrypted Office document utilizing the VelvetSweatshop default password to bypass detection. It contains an embedded OLE object (xl/embeddings/oleObject1.bin) that triggers an Equation Editor exploit. ClamAV specifically identifies this as a downloader for the Formbook malware family.

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.