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

Static analysis result for SHA-256 f3ffc668b39a455b…

MALICIOUS

Office (OLE) / .XLS

199.5 KB Created: 2021-01-20 09:57:17 Authoring application: Microsoft Excel
MD5: 7fc48c36585f7c2e6ea5aa407a880bc5 SHA-1: d9aec5540bb5ab8528c7228144e80c96ef53bfb8 SHA-256: f3ffc668b39a455b981aa7866e87d7a4af8bcb1899ab7e3b6ef7a9191be0ebbd
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1204.002 Malicious File: Malicious File T1059.001 Command and Scripting Interpreter: PowerShell T1105 Ingress Tool Transfer

The critical heuristics OLE_XLM_AUTOOPEN and OLE_XLM_DANGEROUS_FN indicate the presence of an Excel 4.0 macro with an Auto_Open entry that uses dangerous functions. The macro explicitly calls URLDownloadToFileA to download a file from 'https://rebrand.ly/iencli51bat' and saves it as 'C:\PROGRAMDATA\a.bat'. The script then attempts to execute this downloaded batch file.

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
727dfba1ccde0a2892b7d293cc19175678dcc90116d21fc20fec2c150742868d		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 2206 bytes

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