Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 5898329a40dc5c36…

MALICIOUS

Office (OLE) / .XLSX

186.9 KB First seen: 2022-03-18
MD5: cd28de84849e483b6b21fb7dbc9b6435 SHA-1: f777659226661d1ab7017d5d57e4b5aa72830ffe SHA-256: 5898329a40dc5c36f2c03fb99c4a05ddbde28b4610aa1fc264ee8290206679ae
240 Risk Score

Malware Insights

Formbook · confidence 95%

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

The file is a password-encrypted OOXML document identified by ClamAV as Doc.Downloader.Formbook. The presence of an Equation Editor OLE object within the encrypted package strongly suggests it's an exploit carrier. The encryption and malformed structure indicate an attempt to evade static analysis, typical of downloader malware like Formbook.

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.