Name:Allow Inbound Traffic In Firewall Rule id:a5d85486-b89c-11eb-8267-acde48001122 version:4 date:2024-09-30 author:Teoderick Contreras, Splunk status:production type:TTP Description:The following analytic detects a suspicious PowerShell command that allows inbound traffic to a specific local port within the public profile. It leverages PowerShell script block logging (EventCode 4104) to identify commands containing keywords like "firewall," "Inbound," "Allow," and "-LocalPort." This activity is significant because it may indicate an attacker attempting to establish remote access by modifying firewall rules. If confirmed malicious, this could allow unauthorized access to the machine, potentially leading to further exploitation and data exfiltration. Data_source:
-Powershell Script Block Logging 4104
search:`powershell` EventCode=4104 ScriptBlockText = "*firewall*" ScriptBlockText = "*Inbound*" ScriptBlockText = "*Allow*" ScriptBlockText = "*-LocalPort*" | stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer UserID | rename Computer as dest | rename UserID as user | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `allow_inbound_traffic_in_firewall_rule_filter`
how_to_implement:To successfully implement this search, you need to be ingesting logs with the powershell logs from your endpoints. make sure you enable needed registry to monitor this event. known_false_positives:administrator may allow inbound traffic in certain network or machine. References: -https://docs.microsoft.com/en-us/powershell/module/netsecurity/new-netfirewallrule?view=windowsserver2019-ps drilldown_searches: name:'View the detection results for - "$user$" and "$dest$"' search:'%original_detection_search% | search user = "$user$" dest = "$dest$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$user$" and "$dest$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") 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: - 'Prohibited Traffic Allowed or Protocol Mismatch' asset_type:Endpoint confidence:30 impact:10 message:Suspicious firewall modification detected on endpoint $dest$ by user $user$. mitre_attack_id: - 'T1021.001' - 'T1021' observable: name:'user' type:'User' - role: - 'Victim' name:'dest' type:'Hostname' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'EventCode' - 'ScriptBlockText' - 'Computer' - 'UserID' risk_score:3 security_domain:endpoint
