Office (OLE) / .XLSX malware analysis — malicious · 0a21733715c059a8

MALICIOUS

Office (OLE) / .XLSX

250.0 KB Created: 2020-05-27 10:23:52 Authoring application: Microsoft Excel

MD5: faf623d4e2a28671dd4c21626c9c90ff SHA-1: a6cca2bbd05f1c4e7e8f78bd2eae87ff2616a38e SHA-256: 0a21733715c059a8729e9c885a66f32e99ea27f59ce8a3e1d56ea24cf13a3cab

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The file contains critical heuristics indicating the presence of obfuscated Excel 4.0 macros with an Auto_Open execution chain. The macros are designed to be executed automatically upon opening the workbook. The obfuscated formulas suggest an attempt to hide malicious actions, likely involving the download and execution of a second-stage payload. The specific nature of the payload cannot be determined from the provided evidence.

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` `76ef23c5cfc622d486d458c894f7431f60109de5f4cc7c5e65492ea9b5ecd5cb`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	125777 bytes

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