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

Static analysis result for SHA-256 cc8b05dc16d4bcf3…

MALICIOUS

Office (OOXML) / .XLSM

338.0 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 80f8b9a1bbfd7284dc156651ddfb7d84 SHA-1: 947ce444f98e38ab00bac9a2775a922d768df274 SHA-256: cc8b05dc16d4bcf3865d860cf44a0b95cbf0a5db0559aadca892e99231e6d2a4
310 Risk Score

Malware Insights

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

The sample is an XLSM file containing Excel 4.0 macros, which is a known technique for delivering malware. Critical heuristics indicate the use of dangerous XLM functions like FORMULA and RUN, along with strings for WinAPI calls such as URLDownloadToFileA. This strongly suggests the macro's purpose is to download and execute a secondary payload, aligning with the ClamAV detection of Xls.Downloader.IcedID.

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, RUN, HALT, GOTO 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.IcedID-9f1f1d193a2a2a2b-9951463-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.IcedID-9f1f1d193a2a2a2b-9951463-0
  • 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 — context-specific rules above attribute URLs they actually evaluated; this rule lists URLs that were present in the bytes but were not otherwise tied to a specific finding.
    URL http://schemas.openxmlformats.org/spreadsheetml/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/excel/2006/main
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 10

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
fd1b01671c75b39292ebdc4fc2972e3e6068ca4ebc2dd887b7cee03a9c88e291
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3636 bytes
xlm_sheet_01.xml
1468ac10d052bf6caa52b715a135583230c630e9863c2cc5597c81988d95f4dc
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.xml 1756 bytes
xlm_sheet_02.xml
995b390512315ffed16666534397cb6932a97886fa17d78bb2d92fae83357637
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.xml 2219 bytes
xlm_sheet_03.xml
9e27c63eb79aa1a21f51d99c1f994e91655cc33cf5d6d20d1646db125d4a508f
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet4.xml 1569 bytes
xlm_sheet_04.xml
2a837d4ef451240d0866f4ac65bf8a2deb0bac7470e034180f046ef404dfd7fb
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet5.xml 1634 bytes
xlm_sheet_05.xml
4880b2eb84be4b7a139881993b8b5f5ac9706b749d3c9b9bc743b64f1e88a030
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet6.xml 1572 bytes
xlm_sheet_06.xml
b727b5b0e89922534aabbd5127c8e13dff5bfcde7fd64a3dc05b9dee6b4de8e3
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet7.xml 1571 bytes
xlm_sheet_07.xml
8f2343f6b7171d70b8a27bc29094dbf44d70780c2e20fc54af7f2efd63fb1fe4
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet8.xml 1565 bytes
xlm_sheet_08.xml
5d7c7b03d2a655edbd766182c93921d413fd7b066e3733c964ba6b88fde53057
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet9.xml 1571 bytes
xlm_sheet_09.xml
db9aea15e28350f48db9e6e866d86c12b7aa775eb67c14d3dfbb8f7ef583b729
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1368 bytes