Cisco NVM - Webserver Download From File Sharing Website

name: Cisco NVM - Webserver Download From File Sharing Website
id: 1984f997-3b49-4d4b-a7e9-dc5dbf88370e
version: 5
date: '2026-03-10'
author: Nasreddine Bencherchali, Splunk
status: production
type: TTP
description: |
    This analytic detects unexpected outbound network connections initiated by known webserver processes such as `httpd.exe`, `nginx.exe`, or `tomcat.exe` to common file sharing or public content hosting services like GitHub, Discord CDN, Transfer.sh, or Pastebin.
    Webservers are rarely expected to perform outbound downloads, especially to dynamic or anonymous file hosting domains. This behavior is often associated with server compromise,
    where an attacker uses a reverse shell, webshell, or injected task to fetch malware or tools post-exploitation.
    The detection leverages Cisco Network Visibility Module flow data, enriched with process context, to identify this highly suspicious behavior.
data_source:
    - Cisco Network Visibility Module Flow Data
search: |
    `cisco_network_visibility_module_flowdata`
    process_name IN (
        "http*.exe", "nginx*.exe", "php*.exe", "php-cgi*.exe", "tomcat*.exe"
      )
    dest_hostname IN (
        "*.githubusercontent.com*", "*anonfiles.com*", "*cdn.discordapp.com*", "*ddns.net*",
        "*dl.dropboxusercontent.com*", "*ghostbin.co*", "*glitch.me*", "*gofile.io*",
        "*hastebin.com*", "*mediafire.com*", "*mega.nz*", "*onrender.com*", "*pages.dev*",
        "*paste.ee*", "*pastebin.*", "*pastetext.net*", "*privatlab.*",
        "*send.exploit.in*", "*sendspace.com*", "*storage.googleapis.com*",
        "*storjshare.io*", "*supabase.co*", "*temp.sh*", "*transfer.sh*", "*trycloudflare.com*",
        "*ufile.io*", "*w3spaces.com*", "*workers.dev*"
      )
    | 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___webserver_download_from_file_sharing_website_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: |
    In rare cases, a web server may make outbound connections to pull content for legitimate purposes (e.g., downloading templates or updates from a trusted source).
    However, communication to anonymous file-sharing or temporary content domains is strongly suspicious.
    If legitimate use is confirmed, domain- or process-level allowlisting is recommended.
references:
    - https://www.cisa.gov/news-events/alerts/2023/04/13/cisa-adds-3-known-exploited-vulnerabilities-kev-catalog
    - https://www.microsoft.com/en-us/security/blog/2024/01/17/new-ttps-observed-in-mint-sandstorm-campaign-targeting-high-profile-individuals-at-universities-and-research-orgs/
    - https://research.splunk.com/endpoint/4e8391eb-527e-4e39-9a17-c5bde2f89158/
rba:
    message: The host $src$ ran web server process $process_path$ which downloaded content from $dest_hostname$ over port $dest_port$
    risk_objects:
        - field: src
          type: system
          score: 50
    threat_objects:
        - field: process_name
          type: process_name
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 ("$src$") starthoursago=168  | 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: $info_min_time$
      latest_offset: $info_max_time$
tags:
    analytic_story:
        - GhostRedirector IIS Module and Rungan Backdoor
        - Cisco Network Visibility Module Analytics
    asset_type: Endpoint
    mitre_attack_id:
        - T1105
        - T1190
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    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