[metadata]
creation_date = "2023/06/14"
integration = ["endpoint"]
maturity = "production"
min_stack_comments = "The single field New Term rule type used in this rule was added in Elastic 8.4"
min_stack_version = "8.4.0"
updated_date = "2023/10/16"

[rule]
author = ["Elastic"]
description = """
This rule monitors for the execution of several commonly used system commands executed by a previously unknown
executable located in commonly abused directories. An alert from this rule can indicate the presence of potentially 
malicious activity, such as the execution of unauthorized or suspicious processes attempting to run malicious code. 
Detecting and investigating such behavior can help identify and mitigate potential security threats, protecting the 
system and its data from potential compromise.
"""
from = "now-9m"
index = ["logs-endpoint.events.*", "endgame-*"]
language = "kuery"
license = "Elastic License v2"
name = "Suspicious System Commands Executed by Previously Unknown Executable"
note = """## Setup

This rule requires data coming in from Elastic Defend.

### Elastic Defend Integration Setup
Elastic 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.

#### Prerequisite Requirements:
- Fleet is required for Elastic Defend.
- To configure Fleet Server refer to the [documentation](https://www.elastic.co/guide/en/fleet/current/fleet-server.html).

#### The following steps should be executed in order to add the Elastic Defend integration on a Linux System:
- Go to the Kibana home page and click Add integrations.
- In the query bar, search for Elastic Defend and select the integration to see more details about it.
- Click Add Elastic Defend.
- Configure the integration name and optionally add a description.
- Select the type of environment you want to protect, either Traditional Endpoints or Cloud Workloads.
- 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).
- We suggest to select "Complete EDR (Endpoint Detection and Response)" as a configuration setting, that provides "All events; all preventions"
- 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.
For more details on Elastic Agent configuration settings, refer to the [helper guide](https://www.elastic.co/guide/en/fleet/8.10/agent-policy.html).
- Click Save and Continue.
- 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.
For more details on Elastic Defend refer to the [helper guide](https://www.elastic.co/guide/en/security/current/install-endpoint.html).

"""
risk_score = 21
rule_id = "e9001ee6-2d00-4d2f-849e-b8b1fb05234c"
severity = "low"
tags = ["Domain: Endpoint", "OS: Linux", "Use Case: Threat Detection", "Tactic: Execution", "Data Source: Elastic Endgame", "Data Source: Elastic Defend"]
timestamp_override = "event.ingested"
type = "new_terms"

query = '''
host.os.type:linux and event.category:process and event.action:(exec or exec_event or fork or fork_event) and 
process.executable:(
  /bin/* or /usr/bin/* or /usr/share/* or /tmp/* or /var/tmp/* or /dev/shm/* or
  /etc/init.d/* or /etc/rc*.d/* or /etc/crontab or /etc/cron.*/* or /etc/update-motd.d/* or 
  /usr/lib/update-notifier/* or /home/*/.* or /boot/* or /srv/* or /run/*) 
  and process.args:(whoami or id or hostname or uptime or top or ifconfig or netstat or route or ps or pwd or ls) and 
  not process.name:(sudo or which or whoami or id or hostname or uptime or top or netstat or ps or pwd or ls or apt or 
  dpkg or yum or rpm or dnf or dockerd or docker or snapd or snap) and
  not process.parent.executable:(/bin/* or /usr/bin/* or /run/k3s/* or /etc/network/* or /opt/Elastic/*)
'''

[[rule.threat]]
framework = "MITRE ATT&CK"
  
[rule.threat.tactic]
name = "Execution"
id = "TA0002"
reference = "https://attack.mitre.org/tactics/TA0002/"

[[rule.threat.technique]]
name = "Command and Scripting Interpreter"
id = "T1059"
reference = "https://attack.mitre.org/techniques/T1059/"

[[rule.threat.technique.subtechnique]]
name = "Unix Shell"
id = "T1059.004"
reference = "https://attack.mitre.org/techniques/T1059/004/"

[rule.new_terms]
field = "new_terms_fields"
value = ["process.executable"]

[[rule.new_terms.history_window_start]]
field = "history_window_start"
value = "now-14d"