Office (OLE) / .XLSX malware analysis — malicious · 77310ed720b8be1f

MALICIOUS

Office (OLE) / .XLSX

319.0 KB Created: 2020-05-20 11:30:40 Authoring application: Microsoft Excel

MD5: 307a8b7a73e225a5d98613cc6068282e SHA-1: 9333a39f2fdc2d488feef8d51d6404e8eeec9d10 SHA-256: 77310ed720b8be1f42d2e3d70a19376332a1b07fd303cfe5d46e2efe804fd6ab

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristics indicate the presence of obfuscated Excel 4.0 macros with an Auto_Open execution chain. This suggests the file is designed to automatically run malicious code upon opening. No specific family could be identified due to the generic nature of the XLM macros.

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` `2ad7645d2e8e4685520f525eb8cf60a3da2134013eb7ecc67ba94b6cfea372d6`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	127964 bytes

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