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

Static analysis result for SHA-256 1a67cebb408075c1…

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-27 11:42:09 Authoring application: Microsoft Excel
MD5: 32c0ad6d7df66dc5eb328f25523e74ab SHA-1: abb812d5a0ccbe722c3b6447fac0720956287f03 SHA-256: 1a67cebb408075c1a46c5b080164c966c6acc456ba565cbb1dcac0ee061ce760
140 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, specifically an Auto_Open defined name, which is a critical indicator of malicious intent. The presence of the Auto_Open function suggests the macro will execute automatically upon opening the spreadsheet. The heuristics indicate the use of dangerous formula APIs, including the RUN function, which can be used to execute arbitrary commands. While the specific payload is not visible, this mechanism is commonly used for initial access and downloading further stages.

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
85cfb716b9dd84f5fa2ec94c92cb3d4ed54a58e9910352defa1292d871f4bdae
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6843 bytes