Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 ce4f4562d687ae91…

MALICIOUS

Office (OLE) / .XLSX

187.9 KB First seen: 2022-04-06
MD5: d34d1614c196e41de3178643e0986733 SHA-1: e05dd1a2948b9555c2c6fc9e2f6f8a0ee4899a52 SHA-256: ce4f4562d687ae91448c8f66aeb1b0b2f751f45c8f8e688116048a1fa4e8f27b
280 Risk Score

Malware Insights

Formbook · confidence 95%

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

The file is identified as malicious by ClamAV as Doc.Downloader.Formbook. The presence of an Equation Editor OLE object, specifically triggering CVE-2018-0798, indicates the document is designed to exploit this vulnerability. The encrypted nature of the OOXML document further supports its role as an exploit carrier. The malware family is identified as Formbook based on the ClamAV detection name.

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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