Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 2a5027d7c3bb3091…

MALICIOUS

Office (OLE) / .XLSX

186.6 KB First seen: 2022-03-01
MD5: 3e740b9359b8a1c9553c064d204f86d0 SHA-1: c1709cf8c16d87f7bd037edcdb1722b63777f04c SHA-256: 2a5027d7c3bb309150598f506bbffcc1b0a7d94a90056d865b3c715d0932f852
280 Risk Score

Malware Insights

Formbook · confidence 95%

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

This Office document is encrypted and contains an embedded Equation Editor OLE object, which is a known carrier for exploits. Specifically, the 'OLE_EQUATION_EDITOR' and 'CVE_2018_0798_EQUATION_NATIVE_ANOMALY' heuristics indicate exploitation of CVE-2018-0798. The ClamAV detection explicitly identifies the file as 'Doc.Downloader.Formbook', confirming its malicious nature as a downloader for the Formbook family. The document's encrypted nature and the exploit carrier strongly suggest it's designed to trick the user into opening it, leading to the execution of the embedded exploit.

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.