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

Static analysis result for SHA-256 3ad8691efbddbb63…

MALICIOUS

Office (OLE) / .XLS

68.5 KB Created: 2021-01-15 22:22:16 Authoring application: Microsoft Excel
MD5: b9762301d97b235937001fd09f586fb2 SHA-1: 543130c9e1d8eaed85fceaf2b8b802c2c1c8a9c2 SHA-256: 3ad8691efbddbb631e5e285daa5edeaf3431ad9314ed398680064029587f6620
140 Risk Score

Malware Insights

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

The critical heuristics indicate the presence of Excel 4.0 macros with dangerous functions, specifically an Auto_Open entry. The extracted macro script reveals a complex string concatenation to construct a PowerShell command. This command is designed to download a file from 'http://tinyurl.com/y5onncnm' and save it as 'mh.exe' in the user's appdata directory, then execute it. This indicates a downloader or droppper functionality.

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
c86a54b265048d3ae5379c5cbbaf5fe114dc41601acd6db559974db005d675ce
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 1234 bytes