Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 9ed0912a0f13b54a…

MALICIOUS

Office (OLE) / .XLSX

186.7 KB First seen: 2022-03-02
MD5: 3869dbf81e77ad66ba1385bb4eaef2b0 SHA-1: 993a73aa5a6c3f67229a2149e9c5a911733fc9ee SHA-256: 9ed0912a0f13b54a684e1766cc8953d4e87f1017f07c9b9b8331ccbf317ad69f
280 Risk Score

Malware Insights

Formbook · confidence 95%

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

The file is a password-encrypted OOXML document identified as malicious by ClamAV, specifically as Doc.Downloader.Formbook. Heuristics indicate it contains an Equation Editor OLE object (CLSID offset 0x450) with anomalous native stream data, matching the characteristics of CVE-2018-0798. This suggests the document is designed to exploit this vulnerability to download and execute a second-stage payload. The presence of the Equation Editor OLE object and the encryption point to a sophisticated delivery mechanism.

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.

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