Cisco NVM - Suspicious Download From File Sharing Website

name: Cisco NVM - Suspicious Download From File Sharing Website
id: 94ebc001-35e7-4ae8-9b0e-52766b2f99c7
version: 5
date: '2026-03-10'
author: Nasreddine Bencherchali, Splunk
status: production
type: Anomaly
description: |
    This analytic detects suspicious downloads from common file sharing and content delivery platforms using known living-off-the-land binaries (LOLBins)
    such as 'curl.exe', 'certutil.exe', 'msiexec.exe', 'powershell.exe', 'wmic.exe', and others.
    It leverages Cisco Network Visibility Module logs to correlate network flow activity with process context, including command-line arguments, process path,
    and parent process information. These tools are often abused by adversaries and malware to retrieve payloads from public hosting platforms
    such as GitHub, Discord CDN, Transfer.sh, or Pastebin.
    This detection helps identify potential initial access, payload staging, or command and control activity using legitimate services.
data_source:
    - Cisco Network Visibility Module Flow Data
search: |
    `cisco_network_visibility_module_flowdata`
    (
      (process_name = "svchost.exe" process_arguments = "*-s BITS*")
      OR
      process_name IN (
          "curl.exe", "wmic.exe", "wscript.exe", "cscript.exe", "certutil.exe",
          "msiexec.exe", "hh.exe", "powershell.exe", "pwsh.exe", "powershell_ise.exe",
          "installutil.exe", "certoc.exe", "bitsadmin.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___suspicious_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: |
    Some system administrators or development teams may use tools like curl or PowerShell to download files from public services
    for legitimate automation or scripting purposes. However, use of these binaries to contact domains commonly associated with file sharing or temporary hosting
    should be carefully reviewed, as such services are frequently abused by threat actors for malware delivery and staging.
    Tuning by domain allowlisting or internal usage policies is recommended.
references:
    - https://twitter.com/jhencinski/status/1102695118455349248
    - https://isc.sans.edu/forums/diary/Investigating+Microsoft+BITS+Activity/23281/
    - https://www.virustotal.com/gui/domain/paste.ee/relations
    - https://www.cisa.gov/uscert/ncas/alerts/aa22-321a
    - 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/
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: $info_max_time$
rba:
    message: The host $src$ used $process_path$ to download content from the file-sharing domain $dest_hostname$ over port $dest_port$
    risk_objects:
        - field: src
          type: system
          score: 20
    threat_objects:
        - field: process_name
          type: process_name
tags:
    analytic_story:
        - APT37 Rustonotto and FadeStealer
        - Cisco Network Visibility Module Analytics
        - BlankGrabber Stealer
    asset_type: Endpoint
    mitre_attack_id:
        - T1197
    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