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

Static analysis result for SHA-256 1fc85e9a12310ec0…

MALICIOUS

Office (OLE) / .XLSX

49.4 KB First seen: 2022-07-28
MD5: 4ebc86e297006ddeec482c75e1dcd835 SHA-1: bfe4f69376607e25d4e9b5ae50560cd172b8cbe2 SHA-256: 1fc85e9a12310ec020b33d1a9f08ff4a8c7c27656fda05ae64ad333cb8a77c83
262 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File T1059.001 PowerShell T1204 User Execution T1071.001 Web Protocols T1566.001 Spearphishing Attachment

The sample is an encrypted Office document that exploits CVE-2017-0199, a known vulnerability for remote code execution. It contains an embedded URL pointing to a secondary malicious document, indicating it functions as a downloader. The ClamAV detection name 'Xls.Downloader' further supports this assessment.

Heuristics 7

  • OLE2Link / URL Moniker → remote loader — CVE-2017-0199 critical CVE likely CVE_2017_0199
    Document contains an embedded OLE link object whose URL Moniker points to a remote URL. When the host file is opened, Office follows the link, downloads the URL, and processes the response based on its Content-Type (HTA -> mshta.exe, RTF → Word, etc.) — the documented CVE-2017-0199 primitive. The URL extension is not a reliable filter; servers can return different payloads to Office's user agent.
  • 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: 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.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://23.95.52.140/msoffice/doc9/doc9.docx

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