Detection: Cisco NVM - Suspicious Download From File Sharing Website

Updated Date: 2025-07-01 ID: 94ebc001-35e7-4ae8-9b0e-52766b2f99c7 Author: Nasreddine Bencherchali, Splunk Type: Anomaly Product: Splunk Enterprise Security

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.

Search

 1`cisco_network_visibility_module_flowdata`
 2(
 3  (process_name = "svchost.exe" process_arguments = "*-s BITS*")
 4  OR
 5  process_name IN (
 6      "curl.exe", "wmic.exe", "wscript.exe", "cscript.exe", "certutil.exe",
 7      "msiexec.exe", "hh.exe", "powershell.exe", "pwsh.exe", "powershell_ise.exe",
 8      "installutil.exe", "certoc.exe", "bitsadmin.exe"
 9  )
10)
11dest_hostname IN (
12    "*.githubusercontent.com*", "*anonfiles.com*", "*cdn.discordapp.com*", "*ddns.net*",
13    "*dl.dropboxusercontent.com*", "*ghostbin.co*", "*glitch.me*", "*gofile.io*",
14    "*hastebin.com*", "*mediafire.com*", "*mega.nz*", "*onrender.com*", "*pages.dev*",
15    "*paste.ee*", "*pastebin.*", "*pastetext.net*", "*privatlab.*",
16    "*send.exploit.in*", "*sendspace.com*", "*storage.googleapis.com*",
17    "*storjshare.io*", "*supabase.co*", "*temp.sh*", "*transfer.sh*", "*trycloudflare.com*",
18    "*ufile.io*", "*w3spaces.com*", "*workers.dev*"
19  )
20
21| stats count min(_time) as firstTime max(_time) as lastTime
22        values(parent_process_arguments) as parent_process_arguments
23        values(process_arguments) as process_arguments
24        values(parent_process_hash) as parent_process_hash
25        values(process_hash) as process_hash
26        values(module_name_list) as module_name_list
27        values(module_hash_list) as module_hash_list
28        values(dest_port) as dest_port
29        values(aliul) as additional_logged_in_users_list
30        values(dest_hostname) as dest_hostname
31        by src dest parent_process_path parent_process_integrity_level process_path process_name process_integrity_level process_id transport
32
33| `security_content_ctime(firstTime)`
34
35| `security_content_ctime(lastTime)`
36
37| table
38  parent_process_integrity_level parent_process_path parent_process_arguments parent_process_hash
39  process_integrity_level process_path process_name process_arguments process_hash process_id
40  additional_logged_in_users_list module_name_list module_hash_list
41  src dest_hostname dest dest_port transport firstTime lastTime
42
43| `cisco_nvm___suspicious_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___suspicious_download_from_file_sharing_website_filter	`search *`

cisco_nvm___suspicious_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
T1197	BITS Jobs	Defense Evasion

Exploitation

Installation

DE.AE

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 Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

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

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.

Associated Analytic Story

Cisco Network Visibility Module Analytics

Risk Based Analytics (RBA)

Risk Message:

The host $src$ used $process_path$ to download content from the file-sharing domain $dest_hostname$ over port $dest_port$

Risk Object	Risk Object Type	Risk Score	Threat Objects
src	system	30	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