Office (OOXML) / .XLSX malware analysis — malicious · 78c64032693b30a8

MALICIOUS

Office (OOXML) / .XLSX

85.5 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000

MD5: 5cfc1856e3baa348f5e3cdc3466acf21 SHA-1: a5c1f981ae5be29b9fc190fe13cff957dd78b300 SHA-256: 78c64032693b30a80bbbc8e1a47dfb0d90de5f91eb9e495dac9e1b451eb3f9dd

60 Risk Score

Malware Insights

MITRE ATT&CK

T1202 User Execution T1059.001 Command and Scripting Interperter

This sample contains a critical heuristic firing indicating the presence of an Excel 4.0 macro sheet, which is known for executing scripts without user consent. The script appears to construct a path `C:\ProgramData\fnsfunsgrgngkjfgsnd@.rtf`, suggesting it may attempt to read or write data to this location as part of its execution process. Given these indicators, the attack pattern involves leveraging a macro-based mechanism to potentially deliver further payloads or perform unauthorized actions on the host system.

Heuristics 1

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. The macro sheet is stored as XLSB/BIFF12 binary content, which many XML-only OOXML scanners miss.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `755c4d364f03bd5a0c4ca0961a7fc41d416f7e45c60a8787d438b651d9f1cffb`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	4294 bytes

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