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

Static analysis result for SHA-256 33a4ca06e240bb7b…

MALICIOUS

Office (OLE) / .XLSX

1.24 MB
MD5: 58d3107a2b92a5e18c89b78eed4fa5c4 SHA-1: 7fecec69b202cadf12565883cbbcfb4ea8dae8f6 SHA-256: 33a4ca06e240bb7b16a9db28a10d1cb34218970bed0402f5328aadab532fcd1b
200 Risk Score

Malware Insights

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

MITRE ATT&CK
T1204.002 Malicious File: User Execution: Malicious File T1566.001 Phishing: Spearphishing Attachment

The file is an OOXML exploit carrier, specifically an Excel file, that uses default encryption to hide embedded OLE objects. It contains an Equation Editor OLE object which is known to be vulnerable to CVE-2017-11882 and related exploits, indicating it's designed to execute arbitrary code. ClamAV detection further confirms its malicious nature as a downloader.

Heuristics 5

  • 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.
  • 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 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.