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

Static analysis result for SHA-256 9f381cb9a41c723d…

MALICIOUS

Office (OLE) / .XLS

268.0 KB Created: 2021-02-06 22:23:31 Authoring application: Microsoft Excel
MD5: 130739f48418b6bd08537bb8afe3b80e SHA-1: a1966aa5ee7c4ad9a0733f01ea63eeef2b0ebbe0 SHA-256: 9f381cb9a41c723dddeca49ce454e720d3d211968eeef082073cfc531ae361f4
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell T1204.002 Malicious File T1059.005 Visual Basic

The sample contains Excel 4.0 macros, specifically an Auto_Open macro that utilizes the dangerous RUN function. The macro constructs a PowerShell command by concatenating strings and using CHAR() functions to obfuscate the payload. This command is designed to download a file from 'https://tinyurl.com/yajbg9e5' and save it as 'sv.exe' in the user's AppData directory, and then execute it. The macro also includes commands to move the downloaded file and execute it.

Heuristics 3

  • Excel 4.0 Auto_Open defined name critical OLE_XLM_AUTOOPEN_DEFINEDNAME
    oletools recovered an Auto_Open / Auto_Close entry from an Excel 4.0 macro sheet. The raw BIFF name can be tokenized or partially opaque to byte-string checks, but the recovered macro listing confirms the workbook has an XLM auto-execution entry.
  • XLM Auto_Open with dangerous formula APIs critical OLE_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet contains an Auto_Open / Auto_Close entry and dangerous XLM formula APIs that can invoke programs, write files, or transfer control without VBA.
  • Excel 4.0 (XLM) macro sheet present medium OLE_XLM_AUTOOPEN
    Workbook contains an Excel 4.0 macro sheet sub-stream — XLM is rarely seen in modern legitimate workbooks and was a major Office malware vector during 2020-2022.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
9e03e08af21d5c6d150c90eb428e57c19408cfebdfbae9bcf20b48626b4caeb6
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 1242 bytes