GitHub Repo

Detection: Cisco Secure Firewall - SSH Connection to sshd_operns

Updated Date: 2026-01-06 ID: 8a9c1d2e-3f4b-5c6d-7e8f-9a0b1c2d3e4f Author: Nasreddine Bencherchali, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

This analytic detects inbound SSH connections to the sshd_operns service on network devices using Cisco Secure Firewall Intrusion Events. APT actors have been observed enabling sshd_operns and opening it on non-standard ports to maintain encrypted remote access to compromised network infrastructure. This detection leverages Snort signature 65368 to identify connections to this service, which when combined with other indicators may signal persistent access mechanisms established by threat actors.

 1`cisco_secure_firewall` 
 2EventType=IntrusionEvent 
 3signature_id=65368
 4
 5| fillnull
 6
 7| stats dc(signature_id) as unique_signature_count 
 8        values(signature_id) as signature_id 
 9        values(signature) as signature 
10        values(class_desc) as class_desc 
11        values(MitreAttackGroups) as MitreAttackGroups 
12        values(InlineResult) as InlineResult 
13        values(InlineResultReason) as InlineResultReason 
14        values(src) as src 
15        values(dest_port) as dest_port 
16        values(rule) as rule 
17        values(transport) as transport 
18        values(app) as app 
19        min(_time) as firstTime 
20        max(_time) as lastTime 
21        by dest
22
23| `security_content_ctime(firstTime)`
24
25| `security_content_ctime(lastTime)`
26
27| `cisco_secure_firewall___ssh_connection_to_sshd_operns_filter`

Data Source

Name Platform Sourcetype Source
Cisco Secure Firewall Threat Defense Intrusion Event Other 'cisco:sfw:estreamer' 'not_applicable'

Macros Used

Name Value
cisco_secure_firewall sourcetype="cisco:sfw:estreamer"
cisco_secure_firewall___ssh_connection_to_sshd_operns_filter search *
cisco_secure_firewall___ssh_connection_to_sshd_operns_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
T1021.004 SSH Lateral Movement
Exploitation
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 Cisco Secure Firewall Threat Defense Logs, which includes the FileEvent EventType. This search uses an input macro named cisco_secure_firewall. We strongly recommend that you specify your environment-specific configurations (index, source, sourcetype, etc.) for Cisco Secure Firewall Threat Defense 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 Security Cloud (https://splunkbase.splunk.com/app/7404). The malware & file access policy must also enable logging.

Known False Positives

No false positives have been identified yet.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Inbound SSH connection to sshd_operns detected from $src$ to network device $dest$

Risk Object Risk Object Type Risk Score Threat Objects
dest system 50 src

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: 1