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

Static analysis result for SHA-256 91e91ca82d963719…

MALICIOUS

Office (OLE) / .XLSX

229.0 KB
MD5: 174076e22d5f7e23c9dcc97309b3f0a3 SHA-1: 9762d9dc1be6472e1bc9ede05c10ed260f1e5766 SHA-256: 91e91ca82d963719f1c76ed7359ed34b3296901c26709a0ff9145c2a283601c4
220 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution T1027 Obfuscated Files or Information

The sample is a password-encrypted OOXML file using the default 'VelvetSweatshop' password, a common technique to evade detection. It contains an embedded OLE object (xl/embeddings/oleObject1.bin) that triggers CVE-2018-0798 in the Microsoft Equation Editor. The presence of high entropy in the Ole10NatiVE stream suggests the presence of an encrypted or obfuscated payload within the exploit carrier.

Heuristics 6

  • 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.
  • CVE-2018-0798 — anomalous Equation Editor native stream high CVE likely CVE_2018_0798_EQUATION_NATIVE_ANOMALY
    Default-encrypted OOXML contains embedded Equation Editor data with anomalous native stream bytes consistent with a CVE-2018-0798-style exploit. This is treated as likely CVE evidence because the Equation object is malformed and payload-like.
  • 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.
  • 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.
  • 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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