Xls.Downloader.94c25b356b5a6cac-9978798-0 — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 ef44f5f5d5f4e078…

MALICIOUS

Office (OLE) / .XLSX

271.4 KB First seen: 2022-10-28
MD5: 3c460b0ccfb7c2aed06884776593d277 SHA-1: 246ea8f2bd9cc3593557d5b1b60a414544491937 SHA-256: ef44f5f5d5f4e0788abc40ff016c501b6130cb77b653cb1b813b0e1e0d31122b
280 Risk Score

Malware Insights

Xls.Downloader.94c25b356b5a6cac-9978798-0 · confidence 95%

MITRE ATT&CK
T1204 Malicious Link T1204.002 Malicious Link: Malicious File T1059 Command and Scripting Interpreter T1027 Obfuscated Files or Information

The file is a password-encrypted Office document containing an embedded Equation Editor OLE object, which is a known carrier for exploits like CVE-2018-0798. The presence of anomalous Equation Editor native stream data and ClamAV detection as 'Xls.Downloader' strongly indicates that this document is intended to exploit this vulnerability to download and execute a secondary payload. The document's encrypted nature and malformed structure further support its role as a malicious exploit carrier.

Heuristics 7

  • 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.
  • ClamAV: Xls.Downloader.94c25b356b5a6cac-9978798-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.94c25b356b5a6cac-9978798-0
  • 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.
  • 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.