Name:Cisco Secure Firewall - High EVE Threat Confidence id:8c15183e-2e70-4db4-86c3-88f8d9129b66 version:1 date:2025-04-02 author:Nasreddine Bencherchali, Splunk status:production type:Anomaly Description:The following analytic detects connections with a high Encrypted Visibility Engine (EVE) threat confidence score, indicating potentially malicious behavior within encrypted traffic. It leverages Cisco Secure Firewall Threat Defense logs and evaluates the EVE_ThreatConfidencePct field, which reflects the system's confidence in classifying encrypted sessions as threats based on machine learning models and behavioral analysis. A score equal to or greater than 80 suggests the connection is highly likely to be associated with malware command and control (C2), remote access tools, or suspicious tunneling behavior. If confirmed malicious, this may indicate covert communication over TLS from compromised hosts.
Data_source:
search:`cisco_secure_firewall` EventType=ConnectionEvent EVE_ThreatConfidencePct >= 80 | stats count min(_time) as firstTime max(_time) as lastTime Values(rule) as rule Values(url) as url by EVE_Process, EVE_ThreatConfidencePct, src_ip, dest, dest_port, transport, action | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `cisco_secure_firewall___high_eve_threat_confidence_filter`
how_to_implement:This search requires Cisco Secure Firewall Threat Defense Logs, which
includes the ConnectionEvent 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 access policy must also enable logging.
known_false_positives:Some benign applications may exhibit behaviors that resemble encrypted threat patterns, especially if they use uncommon encryption libraries or custom protocols.
Custom-developed or internal tools may trigger high EVE confidence scores depending on how they encrypt data.
It is recommended to validate the associated process (`EVE_Process`) and destination context, and correlate with other logs (e.g., endpoint or threat intel) before taking response action.
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: - 'T1041' - 'T1071.001' - 'T1105' - 'T1573.002' product: - 'Splunk Enterprise' - 'Splunk Cloud' - 'Splunk Enterprise Security'
