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

Static analysis result for SHA-256 1a448a1e70be5d58…

MALICIOUS

Office (OLE) / .XLS

228.0 KB Created: 2020-06-29 02:06:46 Authoring application: Microsoft Excel
MD5: 99623bf981658ae3c9469e59cc94cf75 SHA-1: 5d6557cd5d6591cbbae7e37889b37337e8897059 SHA-256: 1a448a1e70be5d5885d5f527bfca787996eedbd1cb074260129e32e53d934dcf
200 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 User Execution: Malicious File T1105 Ingress Tool Transfer

The sample is an Excel 4.0 (XLM) macro-enabled workbook containing an Auto_Open macro that triggers automatically upon opening. Heuristics indicate the use of dangerous formula APIs (risky-formula=28), which is typical for downloading and executing second-stage payloads. The document body contains a large amount of obfuscated, random-looking string data, which is likely used by the XLM macros to reconstruct a URL or command. The ClamAV detection 'Xls.Dropper.Agent' suggests a dropper functionality.

Heuristics 4

  • 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.
  • ClamAV: Xls.Dropper.Agent-8366166-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Dropper.Agent-8366166-0
  • 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
cafabcf0c8868b0e8e4d59eaa75c42b2f23e970db477bd81121fb61cbd59a9b5		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 132303 bytes

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