Detection: Cisco NVM - Suspicious File Download via Headless Browser

Updated Date: 2025-07-02 ID: cd0e816f-f67d-4dbe-a153-480b546e867e Author: Nasreddine Bencherchali, Splunk Type: TTP Product: Splunk Enterprise Security

Description

This analytic identifies the use of Chromium-based browsers (like Microsoft Edge) running in headless mode with the --dump-dom argument. This behavior has been observed in attack campaigns such as DUCKTAIL, where browsers are automated to stealthily download content from the internet using direct URLs or suspicious hosting platforms. The detection focuses on identifying connections to known file-sharing domains or direct IPs extracted from command-line arguments and cross-checks those against the destination of the flow. Since it leverages Cisco Network Visibility Module telemetry, the rule triggers only if a network connection is made.

Search

 1`cisco_network_visibility_module_flowdata`
 2
 3 ``` Usually the initiator of the connection is the child process, meaning the parent will contain the suspicious command.``` 
 4
 5 (
 6   parent_process_name IN ("brave.exe", "chrome.exe", "msedge.exe", "opera.exe", "vivaldi.exe")
 7   OR
 8   process_name IN ("brave.exe", "chrome.exe", "msedge.exe", "opera.exe", "vivaldi.exe")
 9 )
10 (
11   (parent_process_arguments="*--headless*" parent_process_arguments="*--dump-dom*")
12   OR
13   (process_arguments="*--headless*" process_arguments="*--dump-dom*")
14 )
15 NOT dest IN (
16         "10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16", "100.64.0.0/10", 
17         "127.0.0.0/8", "169.254.0.0/16", "192.0.0.0/24", "192.0.0.0/29", "192.0.0.8/32", 
18         "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32", "192.0.0.171/32", "192.0.2.0/24", 
19         "192.31.196.0/24", "192.52.193.0/24", "192.88.99.0/24", "224.0.0.0/4", "192.175.48.0/24", 
20         "198.18.0.0/15", "198.51.100.0/24", "203.0.113.0/24", "240.0.0.0/4", "::1"
21         )
22
23 ``` In order to avoid matching with any public IP, we extract the IP value from the CommandLine and filter on it```
24
25 
26| rex field=parent_process_arguments "(?i)\\b(?:https?
27|ftp)://(?<extracted_ip_parent>(?:\\d{1,3}\\.){3}\\d{1,3})"
28 
29| rex field=process_arguments "(?i)\\b(?:https?
30|ftp)://(?<extracted_ip_child>(?:\\d{1,3}\\.){3}\\d{1,3})"
31 
32| eval direct_ip_match=if(dest == extracted_ip_child, 1, if(dest == extracted_ip_parent, 1, 0))
33
34 
35| where (
36     dest_hostname IN (
37         "*.githubusercontent.com*", "*anonfiles.com*", "*cdn.discordapp.com*", "*ddns.net*",
38         "*dl.dropboxusercontent.com*", "*ghostbin.co*", "*glitch.me*", "*gofile.io*",
39         "*hastebin.com*", "*mediafire.com*", "*mega.nz*", "*onrender.com*", "*pages.dev*",
40         "*paste.ee*", "*pastebin.*", "*pastetext.net*", "*privatlab.*",
41         "*send.exploit.in*", "*sendspace.com*", "*storage.googleapis.com*",
42         "*storjshare.io*", "*supabase.co*", "*temp.sh*", "*transfer.sh*", "*trycloudflare.com*",
43         "*ufile.io*", "*w3spaces.com*", "*workers.dev*"
44     )
45     OR direct_ip_match = 1
46   )
47
48 
49| stats count min(_time) as firstTime max(_time) as lastTime
50         values(parent_process_arguments) as parent_process_arguments
51         values(process_arguments) as process_arguments
52         values(parent_process_hash) as parent_process_hash
53         values(process_hash) as process_hash
54         values(module_name_list) as module_name_list
55         values(module_hash_list) as module_hash_list
56         values(dest_port) as dest_port
57         values(aliul) as additional_logged_in_users_list
58         values(dest_hostname) as dest_hostname
59         by src dest parent_process_path parent_process_name parent_process_integrity_level process_path process_name process_integrity_level process_id transport
60 
61| `security_content_ctime(firstTime)`
62 
63| `security_content_ctime(lastTime)`
64 
65| table
66   parent_process_integrity_level parent_process_path parent_process_name parent_process_arguments parent_process_hash
67   process_integrity_level process_path process_name process_arguments process_hash process_id
68   additional_logged_in_users_list module_name_list module_hash_list
69   src dest_hostname dest dest_port transport firstTime lastTime
70 
71| `cisco_nvm___suspicious_file_download_via_headless_browser_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_file_download_via_headless_browser_filter	`search *`

cisco_nvm___suspicious_file_download_via_headless_browser_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
T1059	Command and Scripting Interpreter	Execution

Command and Control

Installation

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

Some internal automation frameworks may invoke Chromium browsers in headless mode to programmatically access internal services or webpages. These tools may occasionally download legitimate resources as part of their normal behavior. Tuning based on command-line patterns or known dest hostnames may be required to avoid noise.

Associated Analytic Story

Cisco Network Visibility Module Analytics

Risk Based Analytics (RBA)

Risk Message:

Suspicious file download using the Chromium-based browser $parent_process_name$ via the commandline $process_arguments$. Observed on host $src$ communicating with $dest$ / $dest_hostname$

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