Xls.Downloader.af2fa5c5d0587870-9978799-0 — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 b808aefe238faf5b…

MALICIOUS

Office (OLE) / .XLSX

334.6 KB First seen: 2022-10-20
MD5: e9f48e28742c2c84f4096b2e84af62ac SHA-1: 6b13a8370737625b2b83942fa0364f0117fcba3b SHA-256: b808aefe238faf5b462973b7b8be567b64c17733c065dddb973e586e532a1e12
280 Risk Score

Malware Insights

Xls.Downloader.af2fa5c5d0587870-9978799-0 · confidence 95%

MITRE ATT&CK
T1204 Malicious File T1204.002 Malicious File: User Execution: Malicious Attachment T1059 Command and Scripting Interpreter

The file is an encrypted Excel spreadsheet, identified by ClamAV as Xls.Downloader.af2fa5c5d0587870-9978799-0. Heuristics indicate it contains an Equation Editor OLE object with anomalies consistent with CVE-2018-0798, suggesting it's an exploit carrier designed to download and execute a secondary payload. The document's encrypted nature prevents direct analysis of its content, but the exploit carrier and ClamAV signature strongly indicate malicious intent.

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.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.
  • 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.