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

Static analysis result for SHA-256 4ee6d2f7f560f7ad…

MALICIOUS

Office (OLE) / .XLSX

318.5 KB Created: 2020-05-20 11:44:11 Authoring application: Microsoft Excel
MD5: 71a391504aa67165b018ac30d590a155 SHA-1: f029879cc1a7834f0e426f1df96422a3b03bc0a3 SHA-256: 4ee6d2f7f560f7ad678a481554f3db53d6c86f085ccfbd639515ecc1f3e65c88
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1059.001 PowerShell

The file contains critical heuristics indicating an obfuscated Excel 4.0 macro execution chain, specifically an Auto_Open defined name. The macro code itself is heavily obfuscated using CHAR and arithmetic operations, making it difficult to determine the exact payload. However, the presence of an Auto_Open entry strongly suggests an attempt to automatically execute malicious code upon opening the spreadsheet, likely to download and run a second-stage payload.

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
c0a9634b9125031155b70889f37ce5b19f29676b51934a992de284354faeba1d
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 125988 bytes