Office (OOXML) / .XLSM malware analysis — malicious · 2b0392dfcc308965

MALICIOUS

Office (OOXML) / .XLSM

108.8 KB Created: 2021-02-17 15:42:51 UTC Authoring application: 16.0300

MD5: e9c57550406d15a3eb160cc5f525a6e7 SHA-1: afcd3acaf550dd091276668903447f3bafb08ebc SHA-256: 2b0392dfcc30896508c115c3151c8f15648600996312e7fb728a524bf946f2dd

210 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

This XLSM file contains Excel 4.0 macros, which are known to be used for malicious purposes. The critical heuristic 'OOXML_XLM_DANGEROUS_FN' indicates the use of dangerous XLM formula APIs like RETURN, which can be used to download and execute payloads. The 'OLE_VBA_DOWNLOAD' heuristic further supports this by identifying the use of URLDownloadToFile, a common function for retrieving external content. The presence of hidden sheets also suggests an attempt to conceal malicious activity. The script's primary function appears to be downloading and executing a second-stage payload.

Heuristics 6

URLDownloadToFile in VBA critical OLE_VBA_DOWNLOAD

URLDownloadToFile in VBA
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.
Dangerous XLM formula APIs: RETURN 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.
VBA project inside OOXML medium OOXML_VBA

Document contains vbaProject.bin — VBA macros present
Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET

Excel workbook contains 5 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://schemas.openxmlformats.org/spreadsheetml/2006/main
- http://schemas.microsoft.com/office/excel/2006/main
- http://schemas.openxmlformats.org/officeDocument/2006/relationships
- http://schemas.openxmlformats.org/markup-compatibility/2006
- http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`macros.bas` `a83254af55af80f75423b3b5f57123f4055b5e1d11742e80788dda6fea8e14c4`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	4286 bytes
`vbaProject_00.bin` `a50c8fe2c702023ce9ea98687506552d3e76e8b42eb19795b7ef9b52cbec0569`	vba-project	OOXML VBA project: xl/vbaProject.bin	27136 bytes
`xlm_sheet_00.xml` `033fa5ada161fb6fd4e2352985c513c95a115b027e233285a9a6d70d18d7be8c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	913 bytes

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