LoFP LoFP / 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.

Techniques

Sample rules

Cisco NVM - Webserver Download From File Sharing Website

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.

Detection logic

`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`