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

Static analysis result for SHA-256 04235ce8515fe187…

MALICIOUS

Office (OLE) / .XLS

222.0 KB Created: 2021-02-06 22:23:31 Authoring application: Microsoft Excel
MD5: 1dc63f409700e05a68406cb8e4fd58f6 SHA-1: 66baee25529019ffb69cf9de1a737e6be2868883 SHA-256: 04235ce8515fe187780cc878520784a85794c8d4a4256d86ab6ab31b30f3369a
140 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment

The critical heuristics indicate the presence of Excel 4.0 macros with an Auto_Open entry, which is a common technique for initial execution. The extracted macro script explicitly constructs a PowerShell command to download a file from 'https://tinyurl.com/5yh6vvyk' and save it as 'vs.exe' in the temporary directory, then executes it. This suggests the file acts as a downloader for a second-stage payload.

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
66b8ec5e31036cfe05ef83c1ce4721901d5b2e6d214d1e1103e4f3a19c623162		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 1236 bytes

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