name: Linux Iptables Firewall Modification
id: 309d59dc-1e1b-49b2-9800-7cf18d12f7b7
version: 3
date: '2022-06-03'
author: Teoderick Contreras, Splunk
type: Anomaly
datamodel:
- Endpoint
description: This analytic looks for suspicious commandline that modify the iptables firewall setting of a linux machine.
  This technique was seen in cyclopsblink malware where it modifies the firewall setting of the compromised machine to allow
  traffic to its tcp port that will be used to communicate with its C2 server.
search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes
  where  Processes.process = "*iptables *" AND Processes.process = "* --dport *" AND Processes.process = "* ACCEPT*" AND Processes.process = "*&>/dev/null*"
  AND Processes.process = "* tcp *" AND NOT(Processes.parent_process_path IN("/bin/*", "/lib/*", "/usr/bin/*", "/sbin/*"))
  by Processes.process_name Processes.process Processes.process_id Processes.parent_process_id Processes.process_guid Processes.dest _time span=10s
  Processes.user Processes.parent_process_name  Processes.parent_process_path Processes.process_path
  | rex field=Processes.process "--dport (?<port>3269|636|989|994|995|8443)"
  | stats values(Processes.process) as processes_exec values(port) as ports values(Processes.process_guid) as guids values(Processes.process_id) as pids dc(port) as port_count count 
  by Processes.process_name Processes.parent_process_name Processes.parent_process_id Processes.dest Processes.user Processes.parent_process_path Processes.process_path | where port_count >=3
  | `drop_dm_object_name(Processes)`
  | `security_content_ctime(firstTime)`
  | `security_content_ctime(lastTime)`
  | `linux_iptables_firewall_modification_filter`'
how_to_implement: To successfully implement this search, you need to be ingesting
  logs with the process name, parent process, and command-line executions from your
  endpoints. If you are using Sysmon, you can use the Add-on for Linux Sysmon from
  Splunkbase.
known_false_positives: administrator may do this commandline for auditing and testing purposes.
  In this scenario filter is needed.
references:
- https://www.ncsc.gov.uk/files/Cyclops-Blink-Malware-Analysis-Report.pdf
- https://www.trendmicro.com/en_us/research/22/c/cyclops-blink-sets-sights-on-asus-routers--.html
tags:
  analytic_story:
  - CyclopsBLink
  asset_type: Endpoint
  cis20:
  - CIS 3
  - CIS 5
  - CIS 16
  confidence: 50
  context:
  - Source:Endpoint
  - Stage:Defense Evasion
  dataset:
  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/cyclopsblink/sysmon_linux.log
  impact: 50
  kill_chain_phases:
  - Exploitation
  message: A commandline $process$ that may modify iptables firewall on $dest$
  mitre_attack_id:
  - T1562.004
  - T1562
  nist:
  - DE.CM
  observable:
  - name: dest
    type: Hostname
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - Processes.dest
  - Processes.user
  - Processes.parent_process_name
  - Processes.process_name
  - Processes.process
  - Processes.process_id
  - Processes.parent_process_id
  risk_score: 25
  security_domain: endpoint