Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 dacbe8dcbabe4d8c…

MALICIOUS

Office (OLE) / .XLSX

187.4 KB
MD5: 1541f48821402078d7e32f0a93980710 SHA-1: b051a6e02ecf9650d1a43c69bf038ec0e1c1f62e SHA-256: dacbe8dcbabe4d8c92b362f1953232721bc3906135ea2240108f749937c6a11c
280 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1204 Malicious Link T1566 Phishing T1204.002 Malicious File T1059 Command and Scripting Interpreter

The sample is an encrypted Office document identified by ClamAV as Doc.Downloader.Formbook. Heuristics indicate it contains an Equation Editor OLE object, specifically triggering CVE-2018-0798, which is a known exploit carrier. The document's encrypted nature and the presence of an exploit object strongly suggest it's designed to download and execute a second-stage payload.

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.