Office (OLE) / .XLSX malware analysis — malicious · 5862418c765a003c

MALICIOUS

Office (OLE) / .XLSX

36.0 KB Created: 2020-11-25 10:45:57 Authoring application: Microsoft Excel

MD5: 121eb351932deaab6a65cf57aeb1d22d SHA-1: a62582cc7cd70ca382d28a3cec201af51b443df5 SHA-256: 5862418c765a003c0653f8677f7ed0eae3744968fe8881a97e6d538a56c83574

140 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File

The file contains Excel 4.0 macros, specifically an Auto_Open function, which is a known technique for executing malicious code upon opening the workbook. The critical heuristic firings indicate the presence of dangerous formula APIs, including the RUN function, which is highly suspicious. This suggests the macro is designed to download and execute a second-stage payload. The presence of the RUN function is the primary IOC.

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` `ef7711a448e9094405630ae3ccbd5313f68ab7797b993fd8cb3df3855441ac66`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	6334 bytes

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