ID | Technique | Tactic |
---|---|---|
T1059 | Command and Scripting Interpreter | Execution |
T1071 | Application Layer Protocol | Command And Control |
T1595.002 | Vulnerability Scanning | Reconnaissance |
Detection: Cisco Secure Firewall - High Volume of Intrusion Events Per Host
Description
The following analytic detects internal systems that generate an unusually high volume of intrusion detections within a 30-minute window. It leverages Cisco Secure Firewall Threat Defense logs, specifically focusing on the IntrusionEvent event type, to identify hosts that trigger more than 15 Snort-based signatures during that time. A sudden spike in intrusion alerts originating from a single host may indicate suspicious or malicious activity such as malware execution, command-and-control communication, vulnerability scanning, or lateral movement. In some cases, this behavior may also be caused by misconfigured or outdated software repeatedly tripping detection rules. Systems exhibiting this pattern should be triaged promptly, as repeated Snort rule matches from a single source are often early indicators of compromise, persistence, or active exploitation attempts.
Search
1`cisco_secure_firewall` EventType=IntrusionEvent
2
3| bin _time span=30m
4
5| stats count as TotalEvents values(signature_id) as signature_id
6 values(signature) as signature
7 values(dest) as dest
8 values(dest_port) as dest_port
9 min(_time) as firstTime max(_time) as lastTime
10 by src_ip class_desc MitreAttackGroups InlineResult InlineResultReason rule transport app
11
12| where TotalEvents >= 15
13
14| `security_content_ctime(firstTime)`
15
16| `security_content_ctime(lastTime)`
17
18| `cisco_secure_firewall___high_volume_of_intrusion_events_per_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___high_volume_of_intrusion_events_per_host_filter | search * |
cisco_secure_firewall___high_volume_of_intrusion_events_per_host_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 |
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 can occur in environments where vulnerability scanners or malware sandboxes are actively generating simulated attacks. Additionally, noisy or overly aggressive Snort rules may produce bursts of alerts from legitimate applications. Review host context before escalating.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message:
A high number [$TotalEvents$] of Snort intrusion detections for [$signature$] were triggered by [$src_ip$] in a 30-minute time window.
Risk Object | Risk Object Type | Risk Score | Threat Objects |
---|---|---|---|
src_ip | system | 40 | signature |
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