Office (OLE) / .XLSX malware analysis — malicious · 7c7b2ba9647770f2

MALICIOUS

Office (OLE) / .XLSX

237.5 KB Created: 2020-05-21 07:43:13 Authoring application: Microsoft Excel

MD5: fc86099d05570d1543c4dd0a865ca39d SHA-1: f07340b3f7333e66d73f5cf44d18fdd5e11cdebd SHA-256: 7c7b2ba9647770f2213f724d3cdeaf02cd9e9a984ea2fd790666741623aa1af3

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file contains critical heuristics indicating the presence of obfuscated Excel 4.0 macros with an Auto_Open execution chain. The macro sheet contains a RUN command that likely executes a secondary payload or command, identified as CX48842. The obfuscation and auto-execution suggest a malicious intent to run arbitrary code upon opening the spreadsheet.

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` `d5f5379fb700eb4c5ad5d6306a2fdb08a6b6b1385c1bbc9a9ff9d2aa477de3f9`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	129041 bytes

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