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

Static analysis result for SHA-256 8621bd2ab4555329…

MALICIOUS

Office (OLE) / .XLS

332.0 KB Created: 2006-09-16 00:00:00 Authoring application: Microsoft Excel
MD5: 577b55ca29e7066fdd3b1e950b5e096d SHA-1: 743c109ec46f29d8aef595b4d2af6abe94c43713 SHA-256: 8621bd2ab45553298e02df50162a2b5041f9baa5c8e78d1615104b16e707fdcf
242 Risk Score

Malware Insights

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

The sample is an Excel 4.0 macro-enabled workbook that contains an Auto_Open macro. This macro is designed to execute a series of commands, including a CALL to ShellExecute-like functionality and a RUN command that points to a URL. The macro reconstructs a URL from concatenated strings and also attempts to call external functions, likely to download and execute a second-stage payload. The presence of the Auto_Open macro and the use of dangerous formula APIs indicate a malicious intent to execute arbitrary code.

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.
  • Reference to ShellExecute API high SC_STR_SHELLEXEC
    Reference to ShellExecute API
  • 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://birdexim.com/ds/231120.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
b9e922997ab1008b6d5ca8df5e57db733535c15f4d8d4ecbbf5827b941f024c9		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6069 bytes

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