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

Static analysis result for SHA-256 3529826316922773…

MALICIOUS

Office (OLE) / .XLSX

1.15 MB
MD5: b9b4b1084d93310dcb98e94a6ea40995 SHA-1: 03be6796071424eeef581849b55c28c913ab13b7 SHA-256: 3529826316922773d660f8598e1b5b64de82d5536de77ef8cec5dcadcaf7d3a5
200 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution T1566.001 Phishing: Spearphishing Attachment T1027 Obfuscation

The sample is a malicious Excel file utilizing the 'VelvetSweatshop' default password encryption to bypass scanners. It contains an embedded Equation Editor OLE object with a malformed Ole10Native stream, which is a characteristic signature of the CVE-2017-11882 exploit. No scripts were extracted from this sample, but the structural anomalies and ClamAV detection as a downloader indicate the intent to 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.

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