Cisco NVM - Suspicious Network Connection Initiated via MsXsl

name: Cisco NVM - Suspicious Network Connection Initiated via MsXsl
id: 1cbcf75f-0e45-4f29-8c1b-7fcd7e55cc55
version: 6
creation_date: '2025-07-01'
modification_date: '2026-05-13'
author: Nasreddine Bencherchali, Splunk
status: production
type: Anomaly
description: |
    This analytic identifies the use of `msxsl.exe` initiating a network connection to a non-private IP address.
    Although `msxsl.exe` is a legitimate Microsoft utility used to apply XSLT transformations, adversaries can abuse it
    to execute arbitrary code or load external resources in an evasive manner.
    This detection leverages Cisco NVM telemetry to identify potentially malicious use of `msxsl.exe` making network connections
    that may indicate command and control (C2) or data exfiltration activity.
data_source:
    - Cisco Network Visibility Module Flow Data
search: |
    `cisco_network_visibility_module_flowdata`
    process_name = "msxsl.exe"
    NOT dest IN (
            "10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16", "100.64.0.0/10",
            "127.0.0.0/8", "169.254.0.0/16", "192.0.0.0/24", "192.0.0.0/29", "192.0.0.8/32",
            "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32", "192.0.0.171/32", "192.0.2.0/24",
            "192.31.196.0/24", "192.52.193.0/24", "192.88.99.0/24", "224.0.0.0/4", "192.175.48.0/24",
            "198.18.0.0/15", "198.51.100.0/24", "203.0.113.0/24", "240.0.0.0/4", "::1"
            )
    | stats count min(_time) as firstTime max(_time) as lastTime
            values(parent_process_arguments) as parent_process_arguments
            values(process_arguments) as process_arguments
            values(parent_process_hash) as parent_process_hash
            values(process_hash) as process_hash
            values(module_name_list) as module_name_list
            values(module_hash_list) as module_hash_list
            values(dest_port) as dest_port
            values(aliul) as additional_logged_in_users_list
            values(dest_hostname) as dest_hostname
            by src dest parent_process_path parent_process_integrity_level process_path process_name process_integrity_level process_id transport
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | table
      parent_process_integrity_level parent_process_path parent_process_arguments parent_process_hash
      process_integrity_level process_path process_name process_arguments process_hash process_id
      additional_logged_in_users_list module_name_list module_hash_list
      src dest_hostname dest dest_port transport firstTime lastTime
    | `cisco_nvm___suspicious_network_connection_initiated_via_msxsl_filter`
how_to_implement: |
    This search requires Network Visibility Module logs, which includes the flow data sourcetype.
    This search uses an input macro named `cisco_network_visibility_module_flowdata`.
    We strongly recommend that you specify your environment-specific configurations
    (index, source, sourcetype, etc.) for Cisco Network Visibility Module logs.
    Replace the macro definition with configurations for your Splunk environment.
    The search also uses a post-filter macro designed to filter out known false positives.
    The logs are to be ingested using the Splunk Add-on for Cisco Endpoint Security Analytics (CESA) (https://splunkbase.splunk.com/app/4221).
known_false_positives: |
    False positives may occur in development or administrative environments where msxsl.exe is used
    for legitimate XML transformations. However, its use is uncommon in standard user activity
    and should be reviewed in most environments.
references:
    - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Msxsl/
drilldown_searches:
    - name: View the detection results for - "$src$"
      search: '%original_detection_search% | search  src = "$src$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$src$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: src
          type: system
          score: 20
          message: Host $src$ used msxsl.exe to initiate a suspicious network connection to $dest$
threat_objects:
    - field: process_name
      type: process_name
analytic_story:
    - Cisco Network Visibility Module Analytics
asset_type: Endpoint
mitre_attack_id:
    - T1220
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test - Cisco NVM
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/cisco_network_visibility_module/cisco_nvm_flowdata/nvm_flowdata.log
          source: not_applicable
          sourcetype: cisco:nvm:flowdata
      test_type: unit