Detection: Remote Desktop Network Bruteforce

DEPRECATED DETECTION

This detection has been marked as deprecated by the Splunk Threat Research team. This means that it will no longer be maintained or supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2025-01-10 ID: a98727cc-286b-4ff2-b898-41df64695923 Author: Jose Hernandez, Bhavin Patel, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic has been deprecated in favor of "Windows Remote Desktop Network Bruteforce Attempt". The following analytic identifies potential Remote Desktop Protocol (RDP) brute force attacks by monitoring network traffic for RDP application activity. This query detects potential RDP brute force attacks by identifying source IPs that have made more than 10 successful connection attempts to the same RDP port on a host within a one-hour window. The results are presented in a table that includes the source and destination IPs, destination port, number of attempts, and the times of the first and last connection attempts, helping to prioritize IPs based on the intensity of activity.

Search

1
2| tstats `security_content_summariesonly` count, min(_time) as firstTime, max(_time) as lastTime from datamodel=Network_Traffic where (All_Traffic.app=rdp OR All_Traffic.dest_port=3389) AND All_Traffic.action=allowed by All_Traffic.src, All_Traffic.dest, All_Traffic.dest_port All_Traffic.user All_Traffic.vendor_product  
3| `drop_dm_object_name("All_Traffic")`  
4| eval duration=lastTime-firstTime  
5| where count > 10 AND duration < 3600  
6| `security_content_ctime(firstTime)`  
7| `security_content_ctime(lastTime)`  
8| `remote_desktop_network_bruteforce_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 3	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
remote_desktop_network_bruteforce_filter	`search *`

remote_desktop_network_bruteforce_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
T1110.001	Password Guessing	Credential Access

Exploitation

DE.CM

CIS 13

APT29

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

You must ensure that your network traffic data is populating the Network_Traffic data model. Adjust the count and duration thresholds as necessary to tune the sensitivity of your detection.

Known False Positives

RDP gateways may have unusually high amounts of traffic from all other hosts' RDP applications in the network.Any legitimate RDP traffic using wrong/expired credentials will be also detected as a false positive.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

RDP brute force attack on $dest$

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	25	No Threat Objects

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	Not Applicable	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`

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: 7