Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 802b8793ac7ef59a…

MALICIOUS

Office (OLE) / .XLSX

208.4 KB First seen: 2022-05-10
MD5: 2485216c74c406366a52166cfd70d928 SHA-1: 7de291e508b6f8341ca1d4aed699e8260effd677 SHA-256: 802b8793ac7ef59ac6a78c6dab1d89a9e75d4b3ebe5067433da48add56bc1222
280 Risk Score

Malware Insights

Formbook · confidence 95%

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

The sample is an encrypted Office document that contains an Equation Editor OLE object, which is a known carrier for exploits. Specifically, the 'CVE_2018_0798_EQUATION_NATIVE_ANOMALY' heuristic indicates exploitation of CVE-2018-0798. The ClamAV detection explicitly names the family as 'Formbook', a downloader. The document's encrypted nature and the presence of an exploit carrier strongly suggest it's intended to deliver 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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