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

Static analysis result for SHA-256 fb1ccda3bc1dedd1…

MALICIOUS

Office (OLE) / .XLSX

1.14 MB
MD5: fca0d5bfb87cfc756f93397d1f251ee5 SHA-1: a34cda33877ff023932f148432d50aeb72ee5c84 SHA-256: fb1ccda3bc1dedd150dc4d4a4fdcaa869d970e8aef4f3509dfc7c028cef68ba4
200 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 User Execution: Malicious File T1059 Command and Scripting Interpreter T1203 Exploitation for Client Execution

The sample is an encrypted OOXML file using a default password, which is common in exploit delivery. It contains Equation Editor OLE objects with payload-like anomalies in the Ole10Native stream, indicating a CVE-2017-11882 style exploit. ClamAV detection as a downloader confirms the intent to fetch and execute a second-stage payload.

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.