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

Static analysis result for SHA-256 91dc751a245cd6f6…

MALICIOUS

Office (OLE) / .XLSX

958.0 KB First seen: 2022-04-12
MD5: 8e7cd376f90072b7ab92d327b1c139ad SHA-1: 8008e64118debf6d6b680129671f086f3796ddfd SHA-256: 91dc751a245cd6f67c89f3d2352b1bdd6b08b095ec9202d266bac83ca7435827
220 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File

The sample is a password-encrypted Office document that contains an Equation Editor OLE object. This object is known to be used as a carrier for exploits, and the presence of an anomalous Ole10Native stream within it strongly suggests it is designed to deliver a malicious payload. The encryption and malformed structure further indicate an attempt to evade detection. The specific exploit targeted is likely related to the Equation Editor vulnerability.

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.
  • 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.
  • 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 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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