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

Static analysis result for SHA-256 1a0d129da241bbd4…

MALICIOUS

Office (OLE) / .XLSX

320.0 KB Created: 2020-05-20 11:11:20 Authoring application: Microsoft Excel
MD5: c04df8a7a0be40442a8b740899676cc2 SHA-1: 7689c31aeb32488e3340f3e68870d3b0803765dc SHA-256: 1a0d129da241bbd484de9fc3da3d11c7b090a46f3ca49596f8380a8ff9d016eb
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications

The file contains critical heuristic firings indicating the presence of an obfuscated Excel 4.0 Auto_Open macro. This macro is designed to execute automatically when the workbook is opened. The obfuscation suggests an intent to hide malicious activity, likely to download and execute a secondary payload or perform other harmful actions. No specific family could be identified due to the nature of the XLM macro.

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.
  • Obfuscated XLM Auto_Open execution chain critical OLE_XLM_OBFUSCATED_AUTOEXEC_CHAIN
    Excel 4.0 macro sheet contains an Auto_Open / Auto_Close entry and an obfuscated formula execution chain. The macro builds strings through FORMULA(CHAR(...)), primes state with SET.VALUE / GET.CELL / GOTO, and transfers control through RUN(). This is a high-confidence XLM malware pattern.
  • 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
f894608e06b74adeeac0e41ec3e9e04ae5b0b4443f4068fd57eb8bf537f6f3ba
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 126728 bytes