Office (OOXML) / .XLSX malware analysis — malicious · bc4281dd49f6651a

MALICIOUS

Office (OOXML) / .XLSX

12.9 KB Created: 2020-05-01 16:09:32 UTC Authoring application: Microsoft Excel 16.0300

MD5: 48be1f1540b9ffd903f32f3ab506c144 SHA-1: 4232cf65dfd13f7a76babe43867aa9716237b49c SHA-256: bc4281dd49f6651a0687351c1e03f7233df53ce5155e1040aa56883c187612b3

220 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.003 Windows Command Shell

This OOXML file contains a Workbook_Open macro that utilizes a character-shift decoder to execute a shell command. The presence of the 'auto-exec' heuristic and the critical 'OLE_VBA_SHELL' firing strongly suggest that the macro is designed to download and execute a secondary payload. The VBA code is obfuscated using character-shift decoding, indicating an attempt to evade static analysis.

Heuristics 5

Shell() call in VBA critical OLE_VBA_SHELL

Shell() call in VBA
VBA character-shift decoded Shell command critical OLE_VBA_ASC_CHR_SHIFT_SHELL

VBA auto-exec macro stores an encoded command string, decodes it with a Mid/Asc/Chr character-shift loop, and passes the recovered text to Shell. This is a high-confidence command stager.
Workbook_Open macro high OLE_VBA_WBOPEN

Workbook_Open macro
Suspicious extracted artifact high EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
VBA project inside OOXML medium OOXML_VBA

Document contains vbaProject.bin — VBA macros present

Extracted artifacts 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`macros.bas` `b86f199b0d8b15050e6981aa04fad61597b521455ad46e0017d03915090c4d1b`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	2090 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved macro source contains an auto-exec entry point and execution/download terms.
`vbaProject_00.bin` `852b0e00fffa2673394117b6deea5f2d6cd7e4ef64fbc50e2e13b0aef9ba39a2`	vba-project	OOXML VBA project: xl/vbaProject.bin	14848 bytes

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