Malicious Office (OLE) / .XLSX — malware analysis report

Static analysis result for SHA-256 396f1aa60f34da09…

MALICIOUS

Office (OLE) / .XLSX

164.0 KB First seen: 2022-04-25
MD5: 7705438bc00bd9b1fef97b3582444b2e SHA-1: 3bb7b951bd66374eaa4cebdb7969b1a22654602a SHA-256: 396f1aa60f34da09960d6c4d090fac2797e28ebe8692835de10e982260cae452
220 Risk Score

Malware Insights

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

The file is a password-encrypted Excel spreadsheet, indicated by the OFFICE_ENCRYPTED_PACKAGE and OFFICE_DEFAULT_PASSWORD_ENCRYPTED_OOXML heuristics. The presence of an Equation Editor OLE object (OLE_EQUATION_EDITOR) and specific anomalies related to CVE-2018-0798 (CVE_2018_0798_EQUATION_NATIVE_ANOMALY) strongly suggest it's an exploit carrier. ClamAV detection confirms its malicious nature as a downloader. The primary IOC is the embedded OLE object file, which likely contains the exploit code.

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.
  • 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.
  • ClamAV: Xls.Downloader.94c25b356b5a6cac-9978798-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.94c25b356b5a6cac-9978798-0
  • 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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