Detection: Cisco Secure Firewall - Possibly Compromised Host

EXPERIMENTAL DETECTION

This detection status is set to experimental. The Splunk Threat Research team has not yet fully tested, simulated, or built comprehensive datasets for this detection. As such, this analytic is not officially supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2025-05-02 ID: 244a77bb-3b2a-46f1-bf2c-b4f7cd29276d Author: Nasreddine Bencherchali, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic highlights high-impact intrusion events assigned by Cisco Secure Firewall. This detection leverages Cisco Secure Firewall Threat Defense logs and specifically the IntrusionEvent event type and Impact field assigned by Cisco Secure Firewall looking for an impact score of 1 or 2. If confirmed malicious this may indicate a potential compromised host.

 1`cisco_secure_firewall` EventType=IntrusionEvent Impact IN (1,2)
 2
 3| stats count as TotalDetections values(signature_id) as signature_id 
 4        values(signature) as signature 
 5        values(rule) as rule 
 6        min(_time) as firstTime max(_time) as lastTime 
 7        by src_ip dest dest_port transport Impact app impact_desc class_desc MitreAttackGroups InlineResult InlineResultReason
 8
 9| `security_content_ctime(firstTime)`
10
11| `security_content_ctime(lastTime)`
12
13| `cisco_secure_firewall___possibly_compromised_host_filter`

Data Source

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

Macros Used

Name Value
cisco_secure_firewall sourcetype="cisco:sfw:estreamer"
cisco_secure_firewall___possibly_compromised_host_filter search *
cisco_secure_firewall___possibly_compromised_host_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
T1203 Exploitation for Client Execution Execution
T1059 Command and Scripting Interpreter Execution
T1587.001 Malware Resource Development
Installation
Weaponization
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 IntrusionEvent 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 intrusion access policy must also be configured.

Known False Positives

False positives are directly related to their snort rules triggering and the firewall scoring. Apply additional filters if the rules are too noisy by disabling them or simply ignoring certain IP ranges that trigger it.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

A high impact IntrusionEvent was detected from $src_ip$ to $dest$.

Risk Object Risk Object Type Risk Score Threat Objects
src_ip system 35 signature

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation Not Applicable N/A N/A N/A
Unit ❌ Failing N/A N/A N/A
Integration ❌ Failing N/A N/A N/A

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