Malicious Office (OLE) / .XLS — malware analysis report

Static analysis result for SHA-256 4c3cdfcbc9082f3c…

MALICIOUS

Office (OLE) / .XLS

192.0 KB Created: 2021-02-01 11:09:10 Authoring application: Microsoft Excel
MD5: 1248b2f9c17294757e903e7e589ef227 SHA-1: 5f77bc857f794ceeb767bf51d4d2dd53be225947 SHA-256: 4c3cdfcbc9082f3ceab1cffbf94ad18595f4181d60c6011f980d0cffa60ae153
80 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

The critical heuristic OLE_XLM_AUTOOPEN_DEFINEDNAME indicates the presence of an Excel 4.0 Auto_Open macro. The macro sheet content reveals that it constructs URLs to download an executable and a text file from 'chungasa.com'. It then uses the URLDownloadToFileA function to download the executable to '\ProgramData\q7kiklnu<timestamp>.exe' and subsequently executes it. The macro also attempts to download a text file from 'chungasa.com' to '\ProgramData\q7kiklnu<timestamp>.txt'.

Heuristics 2

  • 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.
  • 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.

FilenameKindSourceSize
xlm_macros.txt
1816553a4aa7382647e843376495edc63abdb8860dfcc7b6f36318bee8f59c15		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 21012 bytes

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