Emotet Office (OLE) / .XLSX malware analysis — malicious · f7c87211a51d435a

MALICIOUS

Office (OLE) / .XLSX

55.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel First seen: 2022-06-23

MD5: 5cb52029263fbb402ac28be10e68ba81 SHA-1: d314841085565c15710beb62f51aa31103320370 SHA-256: f7c87211a51d435a59244b8474de21a0941a2f9f82cd5582e5d3c2003f7c46d4

200 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File

The sample is identified as malicious by ClamAV and exhibits critical heuristic firings for Excel 4.0 macros, specifically an Auto_Open function. The macro sheet contains a concatenated URL, "http://om/random_images/NT5NjK6o/", which is likely used to download and execute a second-stage payload. This behavior is characteristic of Emotet droppers.

Heuristics 4

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.
ClamAV: Xls.Downloader.Emotet-aa87d5786a858772-9953435-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Downloader.Emotet-aa87d5786a858772-9953435-0
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` `540b105993dc412e0ae26dd2ac7093a04067fdf04422a7c06aa311ba2155e2fb`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	8100 bytes

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