Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 d6340431f2222d20…

MALICIOUS

Office (OLE) / .XLSX

224.0 KB First seen: 2022-05-17
MD5: 9cb6fab2d19ad482d65feba352cf9061 SHA-1: f31326906ed4c7e90b9d92f2390460a0c3730383 SHA-256: d6340431f2222d207ca0db27266cec044fe88fc8f30cb8727a539d1516cf9dda
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 Office document, identified by heuristics as an exploit carrier. Specifically, it contains an Equation Editor OLE object, a common technique for exploiting vulnerabilities. ClamAV detection explicitly names this as 'Doc.Downloader.Formbook', indicating its likely family and downloader functionality. The encryption and malformed structure suggest an attempt to evade static analysis while delivering a 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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