Cisco NVM - Suspicious Network Connection From Process With No Args

name: Cisco NVM - Suspicious Network Connection From Process With No Args
id: 54fa06c5-96a2-4406-a4a7-44d93ddbd173
version: 6
creation_date: '2025-07-01'
modification_date: '2026-07-14'
author: Nasreddine Bencherchali, Splunk
status: production
type: Anomaly
description: |
    This analytic detects system binaries that are commonly abused in process injection techniques but are observed without any command-line arguments.
    It leverages Cisco Network Visibility Module (NVM) flow data and process arguments
    to identify outbound connections initiated by curl where TLS checks were explicitly disabled.
    Binaries such as `rundll32.exe`, `regsvr32.exe`, `dllhost.exe`, `svchost.exe`, and others are legitimate Windows processes that are often injected into by malware or post-exploitation frameworks (e.g., Cobalt Strike) to hide execution.
    When these processes are seen initiating a network connection with an empty or missing command line, it can indicate
    potential injection and communication with a command and control server.
data_source:
    - Cisco Network Visibility Module Flow Data
search: |
    `cisco_network_visibility_module_flowdata`
    process_name IN (
      "backgroundtaskhost.exe", "svchost.exe", "dllhost.exe", "werfault.exe",
      "searchprotocolhost.exe", "wuauclt.exe", "spoolsv.exe", "rundll32.exe",
      "regasm.exe", "regsvr32.exe", "regsvcs.exe"
    )
    NOT process_arguments="*"
    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_from_process_with_no_args_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: |
    Some system binaries may execute without arguments in rare legitimate scenarios (e.g., certain service launches), and initiate
    a network connection to microsoft servers for telemetry or update purposes. Apply additional filters as needed.
    However, binaries such as `rundll32.exe` or `dllhost.exe` running with no command-line context are highly suspicious and warrant investigation.
references:
    - https://redcanary.com/threat-detection-report/techniques/process-injection/
intermediate_findings:
    entities:
        - field: src
          type: system
          score: 20
          message: The $process_name$ was seen on host $src$ executing without any command-line arguments and initiating a network connection towards $dest$. This might indicate a potential communication with a C&C server.
threat_objects:
    - field: process_name
      type: process_name
analytic_story:
    - Cisco Network Visibility Module Analytics
asset_type: Endpoint
mitre_attack_id:
    - T1055
    - T1218
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint