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

Static analysis result for SHA-256 21a9fc862611ee16…

MALICIOUS

Office (OLE) / .XLSX

37.0 KB Created: 2020-11-27 11:44:18 Authoring application: Microsoft Excel
MD5: a25ef1bbad7bec1e987a60c1ffc76dc6 SHA-1: b3d170197c39697082a308917f511abca73d81ad SHA-256: 21a9fc862611ee169f998cf1ce6a19de408462c2efba299ebfe28fb7fd1cbe70
140 Risk Score

Malware Insights

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

The file contains Excel 4.0 macro sheets with an Auto_Open defined name, indicating that macros will execute automatically upon opening. The critical heuristic 'OLE_XLM_DANGEROUS_FN' specifically flags the use of dangerous formula APIs like 'RUN=0' within the Auto_Open macro. This strongly suggests the macro is designed to execute arbitrary commands, a common technique for downloading and running secondary payloads. No specific family could be identified, but the execution method points to a macro-based downloader.

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
e97a03254d903935e668c666aa0be335a64b6ed4e48cdc86c1188c965d1494d5
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6798 bytes