Office (OLE) / .XLSX malware analysis — malicious · b320c5fce89bea37

MALICIOUS

Office (OLE) / .XLSX

474.0 KB Created: 2006-09-16 00:00:00 Authoring application: Microsoft Excel

MD5: af7907590f8d19d51208608669eadd47 SHA-1: 2ea418668a8179c44cb458b47d36a1b5915b1546 SHA-256: b320c5fce89bea37082b93e73683f575d0976b1b756a0820cb1b7d04c21ebfb3

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File

The critical heuristics OLE_XLM_AUTOOPEN and OLE_XLM_DANGEROUS_FN indicate the presence of an Excel 4.0 Auto_Open macro. The macro sheet contains a reference to the URL 'http://cssalt.com/examples/cssalt.php', which is likely used to download and execute a second-stage payload. The DOC BODY text appears to be obfuscated or corrupted, but the presence of the URL and the macro structure strongly suggest a malicious downloader.

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.
XLM Auto_Open with dangerous formula APIs critical OLE_XLM_DANGEROUS_FN

Excel 4.0 macro sheet contains an Auto_Open / Auto_Close entry and dangerous XLM formula APIs that can invoke programs, write files, or transfer control without VBA.
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` `ec48c34acde51fff8fc4d0086d45a1a1bc72250aa39b749e9419643eee2d6389`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	20266 bytes

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