Detection: Protocols passing authentication in cleartext

Updated Date: 2025-05-27 ID: 6923cd64-17a0-453c-b945-81ac2d8c6db9 Author: Rico Valdez, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic identifies the use of cleartext protocols that risk leaking sensitive information. It detects network traffic on legacy protocols such as Telnet (port 23), POP3 (port 110), IMAP (port 143), and non-anonymous FTP (port 21). The detection leverages the Network_Traffic data model to identify TCP traffic on these ports. Monitoring this activity is crucial as it can expose credentials and other sensitive data to interception. If confirmed malicious, attackers could capture authentication details, leading to unauthorized access and potential data breaches.

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Network_Traffic where NOT All_Traffic.action IN ("blocked", "block") AND All_Traffic.transport="tcp" AND (All_Traffic.dest_port="23" OR All_Traffic.dest_port="143" OR All_Traffic.dest_port="110" OR (All_Traffic.dest_port="21" AND All_Traffic.user != "anonymous")) by All_Traffic.user All_Traffic.src_ip All_Traffic.dest All_Traffic.dest_port All_Traffic.rule 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `drop_dm_object_name("All_Traffic")` 
6| `protocols_passing_authentication_in_cleartext_filter`

Data Source

Name Platform Sourcetype Source
Cisco Secure Firewall Threat Defense Connection Event N/A 'cisco:sfw:estreamer' 'not_applicable'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
protocols_passing_authentication_in_cleartext_filter search *
protocols_passing_authentication_in_cleartext_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
DE.AE
CIS 13

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 you to be ingesting your network traffic, and populating the Network_Traffic data model. For more accurate result it's better to limit destination to organization private and public IP range, like All_Traffic.dest IN(192.168.0.0/16,172.16.0.0/12,10.0.0.0/8, x.x.x.x/22)

Known False Positives

Some networks may use leverage clear text protocols such as kerberos, FTP or telnet servers. Apply the necessary exclusions where needed.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Allowed Traffic from $src_ip$ to $dest$ over port $dest_port$. Which might indicate a potential authentication attempts over a cleartext protocol.

Risk Object Risk Object Type Risk Score Threat Objects
user user 25 dest
dest system 25 dest

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset not_applicable cisco:sfw:estreamer
Integration ✅ Passing Dataset not_applicable cisco:sfw:estreamer

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: 8