Name:Cisco Secure Firewall - High Volume of Intrusion Events Per Host id:9f2295a0-0dcb-4a5f-b013-8a6f2a3c11f6 version:1 date:2025-04-14 author:Nasreddine Bencherchali, Splunk status:production type:Anomaly 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 In some cases, this behavior may also be caused by misconfigured or outdated software repeatedly tripping detection rules.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.
Data_source:
search:`cisco_secure_firewall` EventType=IntrusionEvent | bin _time span=30m | stats count as TotalEvents values(signature_id) as signature_id values(signature) as signature values(dest) as dest values(dest_port) as dest_port min(_time) as firstTime max(_time) as lastTime by src_ip class_desc MitreAttackGroups InlineResult InlineResultReason rule transport app | where TotalEvents >= 15 | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `cisco_secure_firewall___high_volume_of_intrusion_events_per_host_filter`
how_to_implement: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.
References: -https://www.cisco.com/c/en/us/td/docs/security/firepower/741/api/FQE/secure_firewall_estreamer_fqe_guide_740.pdf drilldown_searches: name:'View the detection results for - "$src_ip$"' search:'%original_detection_search% | search src_ip = "$src_ip$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$src_ip$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src_ip$") starthoursago=168 | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'Cisco Secure Firewall Threat Defense Analytics' asset_type:Network security_domain:network mitre_attack_id: - 'T1059' - 'T1071' - 'T1595.002' product: - 'Splunk Enterprise' - 'Splunk Cloud' - 'Splunk Enterprise Security'
