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

Static analysis result for SHA-256 fb38ea952d38e292…

MALICIOUS

Office (OLE) / .XLSX

114.1 KB First seen: 2022-08-31
MD5: 3a5fdc8df2ab9502b743a6dc3845123f SHA-1: e919a9c167d7808db6183b2b4af59a89a96ac72c SHA-256: fb38ea952d38e2926076a1f2b8ec107b3787d94f2c3bdf5930351be8d9de53be
180 Risk Score

Malware Insights

MITRE ATT&CK
T1204 Malicious Link T1566 Phishing T1204.001 Malicious Link: Malicious Link T1566.001 Phishing: Spearphishing Attachment T1566.002 Phishing: Spearphishing Link

The sample is an encrypted Office XLSX file. Heuristics indicate it is an exploit carrier, specifically leveraging an Equation Editor OLE object. The encryption and malformed structure suggest an attempt to obfuscate malicious content, likely an exploit targeting a known vulnerability.

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.
  • 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.