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

Static analysis result for SHA-256 531f73cbfdc9f235…

MALICIOUS

Office (OLE) / .XLSX

1.25 MB
MD5: 4f84bea2586ff7e7645885d6a94d8f9c SHA-1: 9cc42bc5adf88478683e25d486d11f48d8d76825 SHA-256: 531f73cbfdc9f2353e9b7e6b1ee03d4cb5ea9e4a14716feb0b530494c730aa69
200 Risk Score

Malware Insights

MITRE ATT&CK
T1566.002 Spearphishing Attachment T1204.002 Malicious File

The file is an encrypted Excel spreadsheet that contains an embedded Equation Editor OLE object. This object exhibits anomalies suggesting it carries a payload, and ClamAV has identified it as a downloader. The presence of an Equation Editor OLE object is a strong indicator of exploitation, likely for delivering 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.