Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 30ed1a4e239e9c5d…

MALICIOUS

Office (OLE) / .XLSX

186.1 KB First seen: 2022-03-11
MD5: 81bc01df8a91bc5f1250acd7d57760c8 SHA-1: 33a6691eb721a711099d1f430ce93374bafca455 SHA-256: 30ed1a4e239e9c5d5e6fb41060989cea3ed9be461b9a3843e0f7c912d560b11a
240 Risk Score

Malware Insights

Formbook · confidence 95%

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

The file is identified as malicious by ClamAV with the signature 'Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0', indicating it's a downloader for the Formbook family. The critical heuristics 'OLE_EQUATION_EDITOR' and 'OLE_ENCRYPTED_AND_MALFORMED' point to the exploitation of Equation Editor via an encrypted OLE object within the Excel file. This combination strongly suggests a malicious document designed to exploit vulnerabilities and download further stages.

Heuristics 6

  • 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.
  • 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.