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

Static analysis result for SHA-256 ae24831471f9b684…

MALICIOUS

Office (OLE) / .XLSX

36.5 KB Created: 2020-11-25 10:44:30 Authoring application: Microsoft Excel
MD5: 5815858c5bcf93d99097969a6ec7cb97 SHA-1: b92ed638db51ed7787426c4d12e4b21cc3dc010f SHA-256: ae24831471f9b68440269314cdab39637f5ecffd4da23cbde6a178e27f8a39bf
140 Risk Score

Malware Insights

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

The critical heuristics OLE_XLM_AUTOOPEN and OLE_XLM_DANGEROUS_FN indicate the presence of an Excel 4.0 macro sheet with an Auto_Open entry that uses dangerous functions, specifically the RUN function. This strongly suggests the macro is designed to execute arbitrary commands upon opening the document. The document body contains a large amount of seemingly random characters, which could be obfuscated code or data, further supporting a malicious intent. The presence of an Auto_Open macro is a common technique for initial execution and payload delivery.

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
dbc9dcfa2477c65c1b56996ddedf7b6295618edead4acc6156e39563c4026800
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6689 bytes