Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 7d9c6dc5a440d56a…

MALICIOUS

Office (OLE) / .XLSX

195.7 KB First seen: 2022-04-07
MD5: c0ac0895cb8b6b56b2b41441369e4d7d SHA-1: 3647796bdb31705dd024f3c69d5a348bb2b1c0ce SHA-256: 7d9c6dc5a440d56a4690142773f34e00e8e720bfbfac3cb1fa0a6f8864c2a986
280 Risk Score

Malware Insights

Formbook · confidence 95%

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

The file is identified as malicious by ClamAV as Doc.Downloader.Formbook. Static analysis reveals it is a password-encrypted Office document containing an embedded Equation Editor OLE object. This object exhibits anomalies consistent with CVE-2018-0798, indicating it's designed to exploit this vulnerability. The encryption and malformed structure further suggest it's an exploit carrier. The ClamAV detection name strongly suggests the Formbook family, which is known for its downloader capabilities.

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.