Detection: Cisco NVM - Webserver Download From File Sharing Website

Updated Date: 2025-07-01 ID: 1984f997-3b49-4d4b-a7e9-dc5dbf88370e Author: Nasreddine Bencherchali, Splunk Type: TTP Product: Splunk Enterprise Security

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.

Search

 1`cisco_network_visibility_module_flowdata`
 2process_name IN (
 3    "http*.exe", "nginx*.exe", "php*.exe", "php-cgi*.exe", "tomcat*.exe"
 4  )
 5dest_hostname IN (
 6    "*.githubusercontent.com*", "*anonfiles.com*", "*cdn.discordapp.com*", "*ddns.net*",
 7    "*dl.dropboxusercontent.com*", "*ghostbin.co*", "*glitch.me*", "*gofile.io*",
 8    "*hastebin.com*", "*mediafire.com*", "*mega.nz*", "*onrender.com*", "*pages.dev*",
 9    "*paste.ee*", "*pastebin.*", "*pastetext.net*", "*privatlab.*",
10    "*send.exploit.in*", "*sendspace.com*", "*storage.googleapis.com*",
11    "*storjshare.io*", "*supabase.co*", "*temp.sh*", "*transfer.sh*", "*trycloudflare.com*",
12    "*ufile.io*", "*w3spaces.com*", "*workers.dev*"
13  )
14
15| stats count min(_time) as firstTime max(_time) as lastTime
16        values(parent_process_arguments) as parent_process_arguments
17        values(process_arguments) as process_arguments
18        values(parent_process_hash) as parent_process_hash
19        values(process_hash) as process_hash
20        values(module_name_list) as module_name_list
21        values(module_hash_list) as module_hash_list
22        values(dest_port) as dest_port
23        values(aliul) as additional_logged_in_users_list
24        values(dest_hostname) as dest_hostname
25        by src dest parent_process_path parent_process_integrity_level process_path process_name process_integrity_level process_id transport
26
27| `security_content_ctime(firstTime)`
28
29| `security_content_ctime(lastTime)`
30
31| table
32  parent_process_integrity_level parent_process_path parent_process_arguments parent_process_hash
33  process_integrity_level process_path process_name process_arguments process_hash process_id
34  additional_logged_in_users_list module_name_list module_hash_list
35  src dest_hostname dest dest_port transport firstTime lastTime
36
37| `cisco_nvm___webserver_download_from_file_sharing_website_filter`

Data Source

Name	Platform	Sourcetype	Source
Cisco Network Visibility Module Flow Data	Network	`'cisco:nvm:flowdata'`	`'not_applicable'`

Macros Used

Name	Value
cisco_network_visibility_module_flowdata	`sourcetype="cisco:nvm:flowdata"`
cisco_nvm___webserver_download_from_file_sharing_website_filter	`search *`

cisco_nvm___webserver_download_from_file_sharing_website_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1105	Ingress Tool Transfer	Command And Control
T1190	Exploit Public-Facing Application	Initial Access

Command and Control

Delivery

DE.CM

CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

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.

Associated Analytic Story

Cisco Network Visibility Module Analytics

Risk Based Analytics (RBA)

Risk Message:

The host $src$ ran web server process $process_path$ which downloaded content from $dest_hostname$ over port $dest_port$

Risk Object	Risk Object Type	Risk Score	Threat Objects
src	system	40	process_name

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`not_applicable`	`cisco:nvm:flowdata`
Integration	✅ Passing	Dataset	`not_applicable`	`cisco:nvm:flowdata`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 1