Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 d34fb239eacf1f62…

MALICIOUS

Office (OLE) / .XLSX

186.7 KB First seen: 2022-03-31
MD5: 20cecf3eb06d7a5ef55bee7895ef7b19 SHA-1: 35e18bbffcc818f08bf38519c761adaae6c34ff8 SHA-256: d34fb239eacf1f6233bb429a35c04f8d12ef1f3ec4cc43cab64b3e9d52a2d573
280 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204.002 Malicious File T1559.001 Component Object Model

The sample is an encrypted Office document identified as malicious by ClamAV as Doc.Downloader.Formbook. It contains an Equation Editor OLE object that is anomalous and indicative of CVE-2018-0798. This exploit carrier likely downloads and executes a second-stage payload, consistent with the Formbook family's behavior.

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.