Office (OOXML) / .XLSX malware analysis — malicious · 94bae853353c61ab

MALICIOUS

Office (OOXML) / .XLSX

152.7 KB Created: 2020-04-05 20:26:38 UTC Authoring application: Microsoft Excel 15.0300

MD5: c0acb4308a0740277511341291d2927d SHA-1: 38fdca1d9494a70d38649c44a0875f47386b2f09 SHA-256: 94bae853353c61ab9b5f0ef4539e3d035cefbc3015772a4210ecda2bee2a84c6

340 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059 Command and Scripting Interpreter

This XLSX file contains a Workbook_Open macro that automatically executes. The macro utilizes character-shifting functions (Asc, Chr, Mid) to decode a command, which is then executed using the Shell() function. This indicates a dropper functionality, likely intended to download and execute a second-stage payload, as suggested by the ClamAV detection name 'Xls.Dropper.Agent-7650447-0'.

Heuristics 7

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.
ClamAV: Xls.Dropper.Agent-7650447-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Dropper.Agent-7650447-0
ClamAV detection on extracted artifact critical EXTRACTED_FILE_CLAMAV

ClamAV flagged at least one file extracted from inside this sample. Even when the wrapping document carries no AV detection of its own, a hit on the carved artifact is a strong indicator the sample is a delivery vehicle.
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` `6050018ef14f3ae583e021341b2ea4bf9a449601fb20b5dbd2552ff74898d452`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	4752 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` `d77b0c4e633b9cb6379efa0c03a98d735517264336000f6d5cc9a2f888b1e232`	vba-project	OOXML VBA project: xl/vbaProject.bin	15360 bytes
Detection ClamAV: Xls.Dropper.Agent-7650447-0 Obfuscation or payload: unlikely

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