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

Static analysis result for SHA-256 a2b2a0fd72bf382d…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:39:41 Authoring application: Microsoft Excel
MD5: a21062cc2d23d3643ed5562210f43bcb SHA-1: 4c5d15153b2224c8743621186432e696ef99aa2f SHA-256: a2b2a0fd72bf382dfcdd35f6810bb5efd4392fc116e24e79a4e98e0629ebd140
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1566.001 Spearphishing Attachment

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a known technique for executing malicious code upon opening the spreadsheet. The critical heuristic firings indicate the presence of dangerous formula APIs within the XLM macro, including the RUN function, suggesting the macro is designed to execute arbitrary commands. The macro sheet itself is named 'XCJfAZtyMDcG', which is likely part of the obfuscation or payload delivery mechanism.

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
5d8db707e7d6692022dfa538bc70d974d7fa7b86b53ed37ef25593c44d8ed0df
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6716 bytes