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

Static analysis result for SHA-256 af353e5a45724d8a…

MALICIOUS

Office (OLE) / .XLS

250.5 KB Created: 2020-11-11 04:30:17 Authoring application: Microsoft Excel
MD5: c978fc5f7bc5403f4e4e1711f4f0b31f SHA-1: 7fdd469db22cf229b7c9ff27fb68955a93809c37 SHA-256: af353e5a45724d8ab073afe2a28227992250f0ff12e7f3e4a9fc0307b7d3b3ac
140 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 XLS file containing Excel 4.0 (XLM) macros. Heuristics indicate the use of an Auto_Open macro and dangerous formula APIs (RUN), which is a common pattern for automated payload delivery. The document body contains a large amount of obfuscated or random-looking text, likely used to hide the actual malicious logic or as a filler to bypass detection. No scripts were extracted from the sample, but the presence of XLM macros with auto-execution triggers is highly indicative of a downloader pattern.

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
da383f4b9bb2eb6a7911b29beafc37d09d0cdd9f0c60fa36e64006a3bae1de5e
xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 193609 bytes