Office (OOXML) / .XLSX malware analysis — malicious · 7e866034c442e8a8

MALICIOUS

Office (OOXML) / .XLSX

237.9 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-11

MD5: 4f97c6695485759bb950597726591b83 SHA-1: df6bfbf07c3275e70d919340f06fb2182b80f953 SHA-256: 7e866034c442e8a8d80ea287e1672a1fe31125edb29ba3698eb9ffd0d2e609e0

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an OOXML file containing multiple Excel 4.0 macro sheets, identified by critical heuristics. The embedded macro content is heavily obfuscated and truncated, preventing a detailed analysis of its specific actions. However, the presence of these macros strongly suggests an intent to execute arbitrary code for payload delivery. The ClamAV detection of 'Multios.Malware.Agent-10043485-0' further supports its malicious nature.

Heuristics 3

Excel 4.0 macro sheet (3 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. The macro sheet is stored as XLSB/BIFF12 binary content, which many XML-only OOXML scanners miss.
XLSB international XLM macro sheet hidden in .xlsx critical OOXML_XLSB_INTL_MACROSHEET_IN_XLSX

OOXML package is named .xlsx but contains XLSB workbook parts and an international Excel 4.0 macro sheet. This hides XLM macro execution from scanners that trust the extension or only inspect XML worksheet parts. The technique is macro execution, not a document-parser CVE.
ClamAV: Multios.Malware.Agent-10043485-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Multios.Malware.Agent-10043485-0

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `e544b7ab0da06c170490d3c79fb93c6f6f400c122451cf0debcb64018e387492`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	2504 bytes
`xlm_sheet_01.bin` `294fba96533e16b8e32fcc670b890c44fe9dfc759e5d84743c74026ba7bd4a20`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	428 bytes
`xlm_sheet_02.bin` `f0daf3cbff097906d4170f35f5f5c2394e9b70d2a487782035c708617ae7b9ec`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	428 bytes

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