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

Static analysis result for SHA-256 52c0bda575b4d6c3…

MALICIOUS

Office (OLE) / .XLSX

35.5 KB Created: 2020-11-25 10:41:44 Authoring application: Microsoft Excel
MD5: 5bee46b3168a4ce15664345cfc494cce SHA-1: 353c1614bd4eeb71528b78c4ece782f73360fe95 SHA-256: 52c0bda575b4d6c31671afae7ca02761fc80d13e0c948661eee485b0589f7287
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File

The sample is an Excel file containing Excel 4.0 macros, specifically an Auto_Open macro. This indicates an attempt to automatically execute code when the file is opened. The presence of the Auto_Open macro and the 'RUN' function firing suggests the macro is intended to download and execute a second-stage payload. The document body contains heavily obfuscated and truncated text, making it difficult to determine the exact lure, but the macro execution is the primary malicious behavior.

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
cf507029a746fad1f88ef823c4110b51c89e6e3e21778db88ca2121c1de1a59f
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6550 bytes