GitHub Repo

Detection: Cisco Secure Firewall - SSH Connection to sshd_operns

Updated Date: 2026-02-25 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: 2