Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 f9800d1eecf1f4f1…

MALICIOUS

Office (OLE) / .XLSX

191.1 KB
MD5: c6efe634b0b2db3a221735702d8a7f30 SHA-1: 1c173d13d72d8d7d3d8b7715345229f3564bf1a1 SHA-256: f9800d1eecf1f4f12b9bb83bcc3d03cea980bf1f4abe8afa50969e6c2d89d8d2
280 Risk Score

Malware Insights

Formbook · confidence 95%

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

This Office document is password-encrypted and contains an Equation Editor OLE object, which is a known carrier for exploits. Specifically, the 'CVE_2018_0798_EQUATION_NATIVE_ANOMALY' heuristic indicates a vulnerability in the Equation Editor. The ClamAV detection explicitly names this as 'Doc.Downloader.Formbook', strongly suggesting the Formbook family. The file's structure and heuristics point to it being an exploit carrier designed to download and execute a second-stage payload.

Heuristics 7

  • 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.
  • CVE-2018-0798 — anomalous Equation Editor native stream high CVE likely CVE_2018_0798_EQUATION_NATIVE_ANOMALY
    Default-encrypted OOXML contains embedded Equation Editor data with anomalous native stream bytes consistent with a CVE-2018-0798-style exploit. This is treated as likely CVE evidence because the Equation object is malformed and payload-like.
  • 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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