Decline in host-based traffic

  1[metadata]
  2creation_date = "2025/02/18"
  3integration = ["auditd_manager", "endpoint", "system", "windows"]
  4maturity = "production"
  5min_stack_version = "9.4.0"
  6min_stack_comments = "Use EA (Entity Analytics) fields"
  7updated_date = "2026/07/27"
  8
  9[rule]
 10anomaly_threshold = 75
 11author = ["Elastic"]
 12description = """
 13A machine learning job has detected a sudden drop in host based traffic. This can be due to a range of security issues, such as a compromised system,
 14a failed service, or a network misconfiguration.
 15"""
 16false_positives = [
 17    """
 18    Legitimate causes such as system maintenance, server shutdowns, or temporary network outages may trigger this alert.
 19    """,
 20]
 21from = "now-45m"
 22interval = "5m"
 23license = "Elastic License v2"
 24machine_learning_job_id = "low_count_events_for_a_host_name_ea"
 25name = "Decline in host-based traffic"
 26setup = """## Setup
 27
 28This rule requires the installation of associated Machine Learning jobs, as well as data coming in from one of the following integrations:
 29- Elastic Defend
 30- Auditd Manager
 31- System
 32- Windows
 33
 34### Anomaly Detection Setup
 35
 36Once the rule is enabled, the associated Machine Learning job will start automatically. You can view the Machine Learning job linked under the "Definition" panel of the detection rule. If the job does not start due to an error, the issue must be resolved for the job to commence successfully. For more details on setting up anomaly detection jobs, refer to the [helper guide](https://www.elastic.co/guide/en/kibana/current/xpack-ml-anomalies.html).
 37
 38### Elastic Defend Integration Setup
 39Elastic Defend is integrated into the Elastic Agent using Fleet. Upon configuration, the integration allows the Elastic Agent to monitor events on your host and send data to the Elastic Security app.
 40
 41#### Prerequisite Requirements:
 42- Fleet is required for Elastic Defend.
 43- To configure Fleet Server refer to the [documentation](https://www.elastic.co/guide/en/fleet/current/fleet-server.html).
 44
 45#### The following steps should be executed in order to add the Elastic Defend integration to your system:
 46- Go to the Kibana home page and click "Add integrations".
 47- In the query bar, search for "Elastic Defend" and select the integration to see more details about it.
 48- Click "Add Elastic Defend".
 49- Configure the integration name and optionally add a description.
 50- Select the type of environment you want to protect, either "Traditional Endpoints" or "Cloud Workloads".
 51- Select a configuration preset. Each preset comes with different default settings for Elastic Agent, you can further customize these later by configuring the Elastic Defend integration policy. [Helper guide](https://www.elastic.co/guide/en/security/current/configure-endpoint-integration-policy.html).
 52- We suggest selecting "Complete EDR (Endpoint Detection and Response)" as a configuration setting, that provides "All events; all preventions"
 53- Enter a name for the agent policy in "New agent policy name". If other agent policies already exist, you can click the "Existing hosts" tab and select an existing policy instead.
 54For more details on Elastic Agent configuration settings, refer to the [helper guide](https://www.elastic.co/guide/en/fleet/current/agent-policy.html).
 55- Click "Save and Continue".
 56- To complete the integration, select "Add Elastic Agent to your hosts" and continue to the next section to install the Elastic Agent on your hosts.
 57For more details on Elastic Defend refer to the [helper guide](https://www.elastic.co/guide/en/security/current/install-endpoint.html).
 58
 59### Auditd Manager Integration Setup
 60The Auditd Manager Integration receives audit events from the Linux Audit Framework which is a part of the Linux kernel.
 61Auditd Manager provides a user-friendly interface and automation capabilities for configuring and monitoring system auditing through the auditd daemon. With `auditd_manager`, administrators can easily define audit rules, track system events, and generate comprehensive audit reports, improving overall security and compliance in the system.
 62
 63#### The following steps should be executed in order to add the Elastic Agent System integration "auditd_manager" to your system:
 64- Go to the Kibana home page and click “Add integrations”.
 65- In the query bar, search for “Auditd Manager” and select the integration to see more details about it.
 66- Click “Add Auditd Manager”.
 67- Configure the integration name and optionally add a description.
 68- Review optional and advanced settings accordingly.
 69- Add the newly installed “auditd manager” to an existing or a new agent policy, and deploy the agent on a Linux system from which auditd log files are desirable.
 70- Click “Save and Continue”.
 71- For more details on the integration refer to the [helper guide](https://docs.elastic.co/integrations/auditd_manager).
 72
 73#### Rule Specific Setup Note
 74Auditd Manager subscribes to the kernel and receives events as they occur without any additional configuration.
 75However, if more advanced configuration is required to detect specific behavior, audit rules can be added to the integration in either the "audit rules" configuration box or the "auditd rule files" box by specifying a file to read the audit rules from.
 76- For this detection rule no additional audit rules are required.
 77
 78### System Integration Setup
 79The System integration allows you to collect system logs and metrics from your servers with Elastic Agent.
 80
 81#### The following steps should be executed in order to add the Elastic Agent System integration "system" to your system:
 82- Go to the Kibana home page and click “Add integrations”.
 83- In the query bar, search for “System” and select the integration to see more details about it.
 84- Click “Add System”.
 85- Configure the integration name and optionally add a description.
 86- Review optional and advanced settings accordingly.
 87- Add the newly installed “system” to an existing or a new agent policy, and deploy the agent on your system from which system log files are desirable.
 88- Click “Save and Continue”.
 89- For more details on the integration refer to the [helper guide](https://docs.elastic.co/integrations/system).
 90
 91### Windows Integration Setup
 92The Windows integration allows you to monitor the Windows OS, services, applications, and more.
 93
 94#### The following steps should be executed in order to add the Elastic Agent System integration "windows" to your system:
 95- Go to the Kibana home page and click “Add integrations”.
 96- In the query bar, search for “Windows” and select the integration to see more details about it.
 97- Click “Add Windows”.
 98- Configure the integration name and optionally add a description.
 99- Review optional and advanced settings accordingly.
100- Add the newly installed “windows” to an existing or a new agent policy, and deploy the agent on your system from which windows log files are desirable.
101- Click “Save and Continue”.
102- For more details on the integration refer to the [helper guide](https://docs.elastic.co/integrations/windows).
103"""
104references = ["https://www.elastic.co/guide/en/security/current/prebuilt-ml-jobs.html"]
105risk_score = 21
106rule_id = "ad66db2e-1cc7-4a2c-8fa5-5f3895e44a18"
107severity = "low"
108tags = [
109    "Data Source: Elastic Defend",
110    "Data Source: Auditd Manager",
111    "Data Source: Windows Security Event Logs",
112    "Use Case: Threat Detection",
113    "Rule Type: ML",
114    "Rule Type: Machine Learning",
115    "Resources: Investigation Guide",
116]
117type = "machine_learning"
118note = """## Triage and analysis
119
120> **Disclaimer**:
121> This investigation guide was created using generative AI technology and has been reviewed to improve its accuracy and relevance. While every effort has been made to ensure its quality, we recommend validating the content and adapting it to suit your specific environment and operational needs.
122
123### Investigating Decline in host-based traffic
124
125Host-based traffic monitoring is crucial for identifying anomalies in network activity. A sudden drop in traffic can indicate issues like system compromise, service failure, or misconfiguration. Adversaries might exploit these situations to evade detection or disrupt services. The 'Decline in host-based traffic' rule leverages machine learning to identify unexpected traffic reductions, signaling potential security threats for further investigation.
126
127### Possible investigation steps
128
129- Review the affected host's recent activity logs to identify any unusual patterns or events that coincide with the drop in traffic.
130- Check for any recent changes in network configuration or firewall settings that might have inadvertently caused the traffic decline.
131- Investigate the status of critical services on the host to determine if any have failed or been stopped unexpectedly.
132- Analyze network traffic data to identify any potential signs of compromise, such as connections to known malicious IP addresses or unusual outbound traffic.
133- Consult with system administrators to verify if any maintenance or updates were performed around the time of the traffic drop that could explain the anomaly.
134
135### False positive analysis
136
137- Scheduled maintenance or updates can cause temporary drops in host-based traffic. Users should create exceptions for known maintenance windows to prevent false alerts.
138- Network configuration changes, such as firewall rule updates or routing adjustments, might lead to expected traffic reductions. Document and exclude these changes from triggering alerts.
139- Temporary service outages due to non-security related issues, like hardware failures or software bugs, can be mistaken for threats. Implement monitoring to distinguish between these and actual security incidents.
140- Low-usage periods, such as weekends or holidays, may naturally result in reduced traffic. Adjust the machine learning model to account for these patterns by incorporating historical data.
141- Legitimate changes in user behavior, such as remote work policies or shifts in business operations, can affect traffic levels. Regularly update the model to reflect these changes and avoid false positives.
142
143### Response and remediation
144
145- Isolate the affected host from the network to prevent potential lateral movement or further compromise.
146- Verify the integrity and functionality of critical services on the affected host to identify any failures or misconfigurations.
147- Conduct a thorough malware scan on the isolated host to detect and remove any malicious software.
148- Review recent configuration changes on the host and revert any unauthorized or suspicious modifications.
149- Restore any affected services from known good backups if service failure is confirmed as the cause.
150- Monitor network traffic for any signs of unusual activity or attempts to exploit the situation further.
151- Escalate the incident to the security operations team for a deeper forensic analysis and to determine if additional hosts are affected."""
152
153[[rule.threat]]
154framework = "MITRE ATT&CK"
155
156[[rule.threat.technique]]
157id = "T1562"
158name = "Impair Defenses"
159reference = "https://attack.mitre.org/techniques/T1562/"
160
161[rule.threat.tactic]
162id = "TA0005"
163name = "Defense Evasion"
164reference = "https://attack.mitre.org/tactics/TA0005/"
165
166[[rule.threat]]
167framework = "MITRE ATT&CK"
168
169[[rule.threat.technique]]
170id = "T1489"
171name = "Service Stop"
172reference = "https://attack.mitre.org/techniques/T1489/"
173
174[[rule.threat.technique]]
175id = "T1499"
176name = "Endpoint Denial of Service"
177reference = "https://attack.mitre.org/techniques/T1499/"
178
179[rule.threat.tactic]
180id = "TA0040"
181name = "Impact"
182reference = "https://attack.mitre.org/tactics/TA0040/"