Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 ec7e734dd4e5afa6…

MALICIOUS

Office (OLE) / .XLSX

163.4 KB First seen: 2022-06-28
MD5: cd9ed93259a77ebe343a5e7a4d276a54 SHA-1: 93bfdb0b0f9824ede5cae83ee68f6ccf6542fa19 SHA-256: ec7e734dd4e5afa64d2b4fd3162fd112b5e23d078daf7e4c59d41f8fde818091
280 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204 Malicious File T1204.002 Malicious File: User Execution: Malicious Attachment T1059 Command and Scripting Interpreter

The sample is an encrypted Office document identified by ClamAV as Doc.Downloader.Formbook. It contains an Equation Editor OLE object that exhibits anomalies consistent with CVE-2018-0798, indicating it's an exploit carrier. The encryption and malformed structure suggest an attempt to obfuscate the malicious payload, likely a downloader.

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.