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

Static analysis result for SHA-256 1dc5914a0d62cae2…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:47:31 Authoring application: Microsoft Excel
MD5: c9e68bdcb6a67f84d7d51e2247288887 SHA-1: 280bcbe3b207472789b23efb0140f4a7f4adfca7 SHA-256: 1dc5914a0d62cae2931c4a22e64f63a9296e3c4fecc147f36cddc9ed87bec3aa
140 Risk Score

Malware Insights

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

The sample is an Excel file containing Excel 4.0 macros, specifically an Auto_Open function. This indicates an attempt to automatically execute code upon opening the document. The presence of the Auto_Open defined name and the use of dangerous formula APIs like RUN strongly suggest that this macro is designed to download and execute a second-stage payload. The document body contains obfuscated text, further supporting a malicious intent.

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
fbef88db1388cb0dba9f15b659389e78c46ad463f9e3763fadc320804016467b		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6676 bytes

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