[New Rule] Unusual Linux System Network Configuration Discovery (#265)

* Create ml_linux_system_network_configuration_discovery.toml

ML rule to accompany the network configuration discovery job

* Update ml_linux_system_network_configuration_discovery.toml

added fp field

* Update ml_linux_system_network_configuration_discovery.toml

* Update ml_linux_system_network_configuration_discovery.toml

linting

* Update ml_linux_system_network_configuration_discovery.toml

* Update ml_linux_system_network_configuration_discovery.toml

* Update rules/ml/ml_linux_system_network_configuration_discovery.toml

Co-authored-by: Brent Murphy <56412096+bm11100@users.noreply.github.com>

Co-authored-by: Brent Murphy <56412096+bm11100@users.noreply.github.com>

rules/ml/ml_linux_system_network_configuration_discovery.toml

@@ -0,0 +1,43 @@
+[metadata]
+creation_date = "2020/09/03"
+ecs_version = ["1.6.0"]
+maturity = "production"
+updated_date = "2020/09/03"
+
+[rule]
+anomaly_threshold = 25
+author = ["Elastic"]
+description = """
+Looks for commands related to system network configuration discovery from an unusual user context. This can be due to
+uncommon troubleshooting activity or due to a compromised account. A compromised account may be used by a threat actor
+to engage in system network configuration discovery in order to increase their understanding of connected networks and
+hosts. This information may be used to shape follow-up behaviors such as lateral movement or additional discovery.
+"""
+false_positives = [
+    """
+    Uncommon user command activity can be due to an engineer logging onto a server instance in order to perform manual
+    troubleshooting or reconfiguration.
+    """,
+]
+from = "now-45m"
+interval = "15m"
+license = "Elastic License"
+machine_learning_job_id = "linux_network_configuration_discovery"
+name = "Unusual Linux System Network Configuration Discovery"
+risk_score = 21
+rule_id = "f9590f47-6bd5-4a49-bd49-a2f886476fb9"
+severity = "low"
+tags = ["Elastic", "Linux", "ML"]
+type = "machine_learning"
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1016"
+name = "System Network Configuration Discovery"
+reference = "https://attack.mitre.org/techniques/T1016/"
+
+
+[rule.threat.tactic]
+id = "TA0007"
+name = "Discovery"
+reference = "https://attack.mitre.org/tactics/TA0007/"