Office (OOXML) / .XLSM malware analysis — malicious · b23167419f3c6536

MALICIOUS

Office (OOXML) / .XLSM

411.3 KB Created: 2020-05-22 16:27:36 UTC Authoring application: Microsoft Excel 16.0300

MD5: a9b74341cb1981d5cd91948b0c45226c SHA-1: d532d745158377ed4aa5638fb2155e578576661b SHA-256: b23167419f3c653646c60164aaf08e3fe59fde7831425aa89c43beb38c41c407

380 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File T1083 File and Directory Discovery T1105 Ingress Tool Transfer

This XLSM file contains a Workbook_Open macro that utilizes WScript.Shell to execute a Base64-decoded PowerShell command. This command downloads a second-stage executable named 'nu.exe' from 'http://185.205.209.166/cxwv/nu.exe' to the temporary directory as 'put.exe' and then executes it. The presence of the Workbook_Open macro and the Shell() call strongly indicate a downloader or droppper functionality.

Heuristics 8

Shell() call in VBA critical OLE_VBA_SHELL

Shell() call in VBA
WScript.Shell usage critical OLE_VBA_WSCRIPT

WScript.Shell usage
VBA Base64-decoded Shell command stager critical OLE_VBA_BASE64_SHELL_COMMAND_STAGER

VBA auto-exec macro decodes Base64 string literals into command or script-launch text and executes the result with Shell. This catches cmd/cscript/PowerShell/VBS launchers hidden from plain keyword matching.

URL http://185.205.209.166/cxwv/nu.exe
ClamAV: Xls.Downloader.DridexGreen09213-9890103-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Downloader.DridexGreen09213-9890103-0
Workbook_Open macro high OLE_VBA_WBOPEN

Workbook_Open macro
CreateObject call high OLE_VBA_CREATEOBJ

CreateObject call
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` `ad4a0ec5eb3e54b7384a026a2220b070e685d44c5ea4ee85fe4d002a5c5f69c7`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	2223 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 shell/COM execution token(s). Carved artifact contains 1 long base64-like blob(s). Carved macro source contains an auto-exec entry point and execution/download terms.
`vbaProject_00.bin` `929aed1d885e460e3957fba07c6392b51dd8b3cf61440ea278b0076e5516e492`	vba-project	OOXML VBA project: xl/vbaProject.bin	17920 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 shell/COM execution token(s). Carved artifact contains 1 long base64-like blob(s). Carved macro source contains an auto-exec entry point and execution/download terms.

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