Office (OOXML) / .XLSX malware analysis — malicious · 11a44ba15c5c7017

MALICIOUS

Office (OOXML) / .XLSX

183.4 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300

MD5: a3a8ffa3ee928005d9440a2b042f5aed SHA-1: 3c20e1bc6c9db2c6766409bc925dc2102369dde7 SHA-256: 11a44ba15c5c70173d4a79b34420d466f659f1e768e9673bd99e67f0a85e5ea4

310 Risk Score

Malware Insights

MITRE ATT&CK

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

The sample contains Excel 4.0 macros, evidenced by multiple critical heuristic firings including 'OOXML_XLM_MACROSHEET' and 'OOXML_XLM_DANGEROUS_FN'. These macros utilize the 'URLDownloadToFileA' API to download a payload from one of the provided IP addresses. The presence of 'Auto_Open' defined names and hidden sheets further indicates malicious intent. The macros are designed to download and execute a second-stage payload.

Heuristics 7

Excel 4.0 macro sheet (10 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: FORMULA, GOTO, REGISTER, 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.
Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS

Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.
ClamAV: Xls.Downloader.GreenEnable06210-9869360-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Downloader.GreenEnable06210-9869360-0
Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET

Excel workbook contains 10 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
- http://schemas.microsoft.com/office/spreadsheetml/2014/revision
- http://schemas.microsoft.com/office/spreadsheetml/2015/revision2
- http://schemas.microsoft.com/office/spreadsheetml/2016/revision3
- http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 10

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.xml` `1e56e1f2eede302543e5df8b9ebfaea744b26d28977f1390ea971f4b360a26ef`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml	3222 bytes
`xlm_sheet_01.xml` `9f05fa9be829be1eefeb660a152567edb54f7c357d0db2659790a946134ef9bd`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.xml	1785 bytes
`xlm_sheet_02.xml` `405845b1631a0aa71b486f4418949d96bde2110bb9f06addaf0fcd75e88528c3`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet3.xml	2657 bytes
`xlm_sheet_03.xml` `43e6f6f4ebc87c4132b97fece91322592028938542550327d7113eb1c83010e5`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet4.xml	1849 bytes
`xlm_sheet_04.xml` `49dcda5b792610c41de404d2b70cfc974135ab65a439e8c738a1c9da0fcb9f77`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet5.xml	1771 bytes
`xlm_sheet_05.xml` `d36f154dba963b8e1b114a8eb7856a7559b20af161115ec9858bc4527e63792f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet6.xml	1559 bytes
`xlm_sheet_06.xml` `84c260af46eecb368a56b6975dc52f2fe5cc18e2695b57472a4ec15bdec2c065`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet7.xml	1586 bytes
`xlm_sheet_07.xml` `ad7ce2861628a67d038db82c6e0c4f96565fd87f489a044f5b06b21d72a592e1`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet8.xml	1589 bytes
`xlm_sheet_08.xml` `b58afdef5f0f3f74593fd083f85481e37c174bf42505739468eec6cc33659cb4`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet9.xml	1582 bytes
`xlm_sheet_09.xml` `78202619198b2160503b5dd1d62f26d794ff5905704afedefc7df1582494d5b5`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	1630 bytes

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