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

Static analysis result for SHA-256 1cac8d785e56b236…

MALICIOUS

Office (OLE) / .XLSX

145.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: f091c05cee55d1efb914cdf78a7c7eb2 SHA-1: 871099c5152c0e2f57737603f0f7a8318d4433be SHA-256: 1cac8d785e56b23615f03a23d7a0b6c58f9547b5e4487f3304b88a502db269db
262 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File

The file contains Excel 4.0 macros, specifically an Auto_Open macro, which is a critical indicator of malicious intent. The macros are designed to reconstruct and execute URLs, such as 'http://lupus.ktcatl.com/wp-content/uCccWJ/', to download and run a second-stage payload. The presence of 'RegisterServer' and 'Dl' strings within the macro further suggests a downloader functionality. ClamAV also detected this as 'Doc.Downloader.EmotetRed02222-9938635-0'.

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 (5 URLs) 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) or across individual numeric cells (one ASCII charcode per cell). 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 plus LABELSST/RK/NUMBER cells.
  • ClamAV: Doc.Downloader.EmotetRed02222-9938635-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.EmotetRed02222-9938635-0
  • 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 http://lupus.ktcatl.com/wp-content/uCccWJ/
    • https://packersandmoversbangalorecharges.com/cgi-bin/UrI6GM87K5u2y2pOW/
    • http://123breathe.org/error/Drs/
    • https://greenesqualityflooring.com/error/kUO7NnkpMp2cs/
    • http://new.hssus.org/wp-includes/blocks/eKID0QAfLUS/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
1574ee13450fd34682012e2ebea7c020d326605272204fb688e7873d4a7c8165		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6756 bytes

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