Office (OLE) / .XLSX malware analysis — malicious · 64f12956cf703d7b

MALICIOUS

Office (OLE) / .XLSX

246.5 KB Created: 2020-05-22 10:54:10 Authoring application: Microsoft Excel

MD5: 82c12e7fe6cabf5edc0bdaa760b4b8c8 SHA-1: 8d34428fbb47908be6486446238967ce494793d2 SHA-256: 64f12956cf703d7b32f1967b884fbd790c6141eabf88bc84c12b20403b8fc708

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file contains obfuscated Excel 4.0 macros, indicated by critical heuristic firings for OLE_XLM_AUTOOPEN and OLE_XLM_OBFUSCATED_AUTOEXEC_CHAIN. The Auto_Open entry suggests an attempt to automatically execute malicious code upon opening the spreadsheet. The obfuscation makes it difficult to determine the exact payload, but the presence of an auto-executing macro chain is a strong indicator of malicious intent.

Heuristics 3

Excel 4.0 Auto_Open defined name critical OLE_XLM_AUTOOPEN_DEFINEDNAME

oletools recovered an Auto_Open / Auto_Close entry from an Excel 4.0 macro sheet. The raw BIFF name can be tokenized or partially opaque to byte-string checks, but the recovered macro listing confirms the workbook has an XLM auto-execution entry.
Obfuscated XLM Auto_Open execution chain critical OLE_XLM_OBFUSCATED_AUTOEXEC_CHAIN

Excel 4.0 macro sheet contains an Auto_Open / Auto_Close entry and an obfuscated formula execution chain. The macro builds strings through FORMULA(CHAR(...)), primes state with SET.VALUE / GET.CELL / GOTO, and transfers control through RUN(). This is a high-confidence XLM malware pattern.
Excel 4.0 (XLM) macro sheet present medium OLE_XLM_AUTOOPEN

Workbook contains an Excel 4.0 macro sheet sub-stream — XLM is rarely seen in modern legitimate workbooks and was a major Office malware vector during 2020-2022.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_macros.txt` `54b177bdedbcf932a99ac15f2f4abb3a40666bf6e400439ff8243da55ca11d71`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	126869 bytes

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