sigma-rules/rules/linux/execution_shell_via_suspicious_binary.toml

[metadata]
creation_date = "2023/07/05"
integration = ["endpoint"]
maturity = "production"
min_stack_comments = "New fields added: required_fields, related_integrations, setup"
min_stack_version = "8.3.0"
updated_date = "2023/08/10"

[rule]
author = ["Elastic"]
description = """
This detection rule detects the creation of a shell through a chain consisting of the execution of a suspicious binary
(located in a commonly abused location or executed manually) followed by a network event and ending with a shell being
spawned. Stageless reverse tcp shells display this behaviour. Attackers may spawn reverse shells to establish 
persistence onto a target system.
"""
from = "now-9m"
index = ["logs-endpoint.events.*"]
language = "eql"
license = "Elastic License v2"
name = "Potential Reverse Shell via Suspicious Binary"
references = [
    "https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Methodology%20and%20Resources/Reverse%20Shell%20Cheatsheet.md"
]
risk_score = 47
rule_id = "fa3a59dc-33c3-43bf-80a9-e8437a922c7f"
severity = "medium"
tags = ["Domain: Endpoint", "OS: Linux", "Use Case: Threat Detection", "Tactic: Execution"]
type = "eql"
query = '''
sequence by host.id, process.entity_id with maxspan=1s
[ process where host.os.type == "linux" and event.type == "start" and event.action == "exec" and
  process.executable : (
  "./*", "/tmp/*", "/var/tmp/*", "/var/www/*", "/dev/shm/*", "/etc/init.d/*", "/etc/rc*.d/*",
  "/etc/crontab", "/etc/cron.*", "/etc/update-motd.d/*", "/usr/lib/update-notifier/*",
  "/boot/*", "/srv/*", "/run/*", "/root/*", "/etc/rc.local"
   ) and
  process.parent.name : ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish") and not
  process.name : ("curl", "wget", "ping", "apt", "dpkg", "yum", "rpm", "dnf", "dockerd") ]
[ network where host.os.type == "linux" and event.type == "start" and event.action in ("connection_attempted", "connection_accepted") and
  process.executable : (
  "./*", "/tmp/*", "/var/tmp/*", "/var/www/*", "/dev/shm/*", "/etc/init.d/*", "/etc/rc*.d/*",
  "/etc/crontab", "/etc/cron.*", "/etc/update-motd.d/*", "/usr/lib/update-notifier/*",
  "/boot/*", "/srv/*", "/run/*", "/root/*", "/etc/rc.local"
   ) and destination.ip != null and destination.ip != "127.0.0.1" and destination.ip != "::1" ]
[ process where host.os.type == "linux" and event.action == "exec" and event.type == "start" and 
  process.name : ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish") and 
  process.parent.name : ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish") ]
'''

[[rule.threat]]
framework = "MITRE ATT&CK"

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

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

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

[[rule.threat]]
framework = "MITRE ATT&CK"

[rule.threat.tactic]
name = "Command and Control"
id = "TA0011"
reference = "https://attack.mitre.org/tactics/TA0011/"

[[rule.threat.technique]]
name = "Application Layer Protocol"
id = "T1071"
reference = "https://attack.mitre.org/techniques/T1071/"