Malicious Office (OOXML) / .XLSM — malware analysis report

Static analysis result for SHA-256 6d8618f80b90e900…

MALICIOUS

Office (OOXML) / .XLSM

231.0 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 16103f1f626df1b96e109ae784da2433 SHA-1: ca0454f33b79d8cd5d910dac613dd3f09fbb6eb7 SHA-256: 6d8618f80b90e900aed8ea11e9f19dd8dbe59005f1d744bd1315a6493eb52fc7
218 Risk Score

Malware Insights

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

The sample is an XLSM file containing Excel 4.0 macros, which is a strong indicator of malicious intent. The document body explicitly prompts the user to 'PLEASE ENABLE MACROS FOR EDIT AND VIEW', acting as a lure. The embedded Excel 4.0 macro sheet uses dangerous functions like FOPEN and EXEC to write and execute a script from the path 'C:\ProgramData\KNFuKr.sct'. This indicates the file's primary purpose is to download and execute a second-stage payload.

Heuristics 7

  • Excel 4.0 macro sheet (1 sheet(s)) critical OOXML_XLM_MACROSHEET
    Spreadsheet contains an Excel 4.0 (XLM) macro sheet — XLM was a major Office malware vector during 2020-2022 and evaded many VBA-focused controls before Microsoft tightened XLM defaults. Even legitimate XLM use is rare in modern workbooks.
  • Excel 4.0 Auto_Open defined name critical OOXML_XLM_AUTOOPEN_DEFINEDNAME
    Workbook defines _xlnm.Auto_Open or _xlnm.Auto_Close while containing an XLM macro sheet. This is the OOXML/XLSB auto-execution shape for Excel 4.0 macros.
  • Dangerous XLM formula APIs: FOPEN, FWRITE, FCLOSE, EXEC, HALT critical OOXML_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet uses formula APIs that call directly into Win32 (=CALL/=EXEC/=REGISTER/=FORMULA). These are the primitives used to download payloads, write files, and start processes from an XLM macro without invoking VBA.
  • Macro/content-enable lure medium SE_ENABLE_LURE
    Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings
  • External hyperlinks (1) low OOXML_EXTERNAL_HYPERLINKS
    Document contains 1 external hyperlink — clickable URLs are stored as external relationships. First target: http://www.shipco.com/ecommerce/sch/scheduleindex.php
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 1 hidden sheet(s) — hidden sheets are commonly used to conceal macro code, staging data, or intermediate payload construction
  • 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://www.shipco.com/ecommerce/sch/scheduleindex.php
    • http://schemas.openxmlformats.org/spreadsheetml/2006/main
    • http://schemas.microsoft.com/office/excel/2006/main
    • http://schemas.openxmlformats.org/officeDocument/2006/relationships

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
bc7f7d01670c3f4bdade469ebc380dfdb9bf356494c5d76d24c34b2bd2da2d27		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 983713 bytes

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