:warning: THIS IS A EXPERIMENTAL DETECTION

This detection has been marked experimental by the Splunk Threat Research team. This means we have not been able to test, simulate, or build datasets for this detection. Use at your own risk. This analytic is NOT supported.

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Description

The following analytic identifies potential Remote Desktop Protocol (RDP) brute force attacks by monitoring network traffic for RDP application activity. It detects anomalies by filtering source and destination pairs that generate traffic exceeding twice the standard deviation of the average traffic. This method leverages the Network_Traffic data model to identify unusual patterns indicative of brute force attempts. This activity is significant as it may indicate an attacker attempting to gain unauthorized access to systems via RDP. If confirmed malicious, this could lead to unauthorized access, data exfiltration, or further network compromise.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Network_Traffic
  • Last Updated: 2024-05-17
  • Author: Jose Hernandez, Splunk
  • ID: a98727cc-286b-4ff2-b898-41df64695923

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1021.001 Remote Desktop Protocol Lateral Movement
T1021 Remote Services Lateral Movement
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 13
CVE 


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| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Network_Traffic where All_Traffic.app=rdp by All_Traffic.src All_Traffic.dest All_Traffic.dest_port 
| eventstats stdev(count) AS stdev avg(count) AS avg p50(count) AS p50 
| where count>(avg + stdev*2) 
| rename All_Traffic.src AS src All_Traffic.dest AS dest 
| table firstTime lastTime src dest count avg p50 stdev 
| `remote_desktop_network_bruteforce_filter`

Macros

The SPL above uses the following Macros:

:information_source: remote_desktop_network_bruteforce_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • All_Traffic.app
  • All_Traffic.src
  • All_Traffic.dest
  • All_Traffic.dest_port

How To Implement

You must ensure that your network traffic data is populating the Network_Traffic data model.

Known False Positives

RDP gateways may have unusually high amounts of traffic from all other hosts' RDP applications in the network.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
25.0 50 50 $dest$ may be the target of an RDP Bruteforce

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 3