Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 55951ac49f5792d8…

MALICIOUS

Office (OLE)

200.5 KB Created: 2018-12-19 10:42:12 Authoring application: Microsoft Excel First seen: 2020-02-04
MD5: e740ae535cae87345218e528b7825746 SHA-1: ae4c29c3ae343c1f96397700ad20db3e1e63fc38 SHA-256: 55951ac49f5792d8c1bfb0072db56895ab5b290b531ed8803b809b62e1f4f3cb
262 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

This Excel 4.0 macro-enabled document contains an Auto_Open macro that executes msiexec.exe to download and run payloads from two URLs. The macro uses dangerous formula APIs, specifically the RUN function, to achieve this. The ClamAV detection 'Xls.Dropper.Agent-7002536-0' further confirms its malicious nature.

Heuristics 6

  • ClamAV: Xls.Dropper.Agent-7002536-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Dropper.Agent-7002536-0
  • 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 (2 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), 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.
  • 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://engast.top/rt1 Referenced by macro
    • http://lecmess.top/dat1Referenced by macro

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 1852 bytes
SHA-256: c9b9d78dcd1a9fc6958870c174017989850ed71f5e020f73449a2ea278f33049
Preview script
First 1,000 lines of the extracted script
' 0085      9 BOUNDSHEET : Sheet Information - Excel 4.0 macro sheet, hidden -  
' 0085     13 BOUNDSHEET : Sheet Information - worksheet or dialog sheet, hidden -  Page
' 0085     11 BOUNDSHEET : Sheet Information - worksheet or dialog sheet, visible -    
' 0018     31 LABEL : Cell Value, String Constant - breakout1 len=7 ptgRef3d  !E4 
' 0018     31 LABEL : Cell Value, String Constant - breakout2 len=7 ptgRef3d  !F10 
' 0018     28 LABEL : Cell Value, String Constant - Labos1 len=7 ptgRef3d  !E4 
' 0018     28 LABEL : Cell Value, String Constant - Labos2 len=7 ptgRef3d  !F10 
' 0018     28 LABEL : Cell Value, String Constant - Macro1 len=7 ptgRef3d  !E4 
' 0018     28 LABEL : Cell Value, String Constant - Macro2 len=7 ptgRef3d  !F10 
' 0018     23 LABEL : Cell Value, String Constant - built-in-name 1 Auto_Open len=7 ptgRef3d  !D2 
' 002a      2 PRINTHEADERS : Print Row/Column Labels
' 00fd     10 LABELSST : Cell Value, String Constant/ SST
' 00fd     10 LABELSST : Cell Value, String Constant/ SST
' 00fd     10 LABELSST : Cell Value, String Constant/ SST
' 00fd     10 LABELSST : Cell Value, String Constant/ SST
' 00fd     10 LABELSST : Cell Value, String Constant/ SST
' 00fd     10 LABELSST : Cell Value, String Constant/ SST
' 00fd     10 LABELSST : Cell Value, String Constant/ SST
' 00fd     10 LABELSST : Cell Value, String Constant/ SST
' 002a      2 PRINTHEADERS : Print Row/Column Labels
' 002a      2 PRINTHEADERS : Print Row/Column Labels
' Sheet,Reference,Formula,Value
'  ,D2,breakout1(),""
'  ,D3,HALT(),""
'  ,E5,breakout2(),""
'  ,E8,RETURN(),""
'  ,F11,IF(L2+M2>0),""
'  ,F13,"EXEC( !A32,2)",""
'  ,F14,"MESSAGE(TRUE,"Done")",""
'  ,F20,*STACKERROR* not enough arguments for function: ELSE,""
'  ,F21,PAUSE(),""
'  ,F23,*STACKERROR* not enough arguments for function: END.IF,""
'  ,F24,RETURN(),""
'  ,A33,HALT(),""

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