Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 51091d0bd503f9f0…

MALICIOUS

Office (OLE) / .XLSX

183.7 KB First seen: 2022-05-12
MD5: 1c412deeeea71fcca48a22cbe110b611 SHA-1: fd7c36d2845ba830b67741a98a5a66d81d8aed6a SHA-256: 51091d0bd503f9f0bae0979de7bd8d7aad4c9b46671b035c7ef3b1b74917af34
240 Risk Score

Malware Insights

Formbook · confidence 95%

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

The file is an encrypted Office document, identified by ClamAV as Doc.Downloader.Formbook. The presence of an Equation Editor OLE object within an encrypted OOXML structure strongly suggests it's an exploit carrier. This combination is characteristic of malware delivery, likely aiming to exploit vulnerabilities via the Equation Editor to download and execute a secondary payload.

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.