Xls.Downloader.af2fa5c5d0587870-9978799-0 — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 66ee6a3c2a36b8e0…

MALICIOUS

Office (OLE) / .XLSX

1.14 MB
MD5: 95477d3439411e6aa6704a73a3bb6c05 SHA-1: 608d09e4548450ebd3d9b21869836a36510b0f7f SHA-256: 66ee6a3c2a36b8e0271b94dd89258bfcbfffc72b3b1c689bc8dadfbba3970b95
280 Risk Score

Malware Insights

Xls.Downloader.af2fa5c5d0587870-9978799-0 · confidence 95%

MITRE ATT&CK
T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The file is an encrypted OOXML document that contains an Equation Editor OLE object. This object carries a payload within its Ole10Native stream, indicating it's designed to exploit a vulnerability like CVE-2017-11882 for client execution. The ClamAV detection name 'Xls.Downloader' further supports its role as 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.
  • 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.af2fa5c5d0587870-9978799-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.af2fa5c5d0587870-9978799-0
  • 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.
  • Equation Editor object carries payload-like Ole10Native stream high OLE_EQUATION_OLE10NATIVE_PAYLOAD_ANOMALY
    Default-encrypted OOXML embedded OLE object declares the Equation Editor CLSID but stores a large high-entropy Ole10Native stream with malformed package sizing. This is exploit-shaped Equation/OLE payload evidence.
  • 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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