LoFP LoFP / administrator may do this commandline for auditing and testing purposes. in this scenario filter is needed.

Techniques

Sample rules

Linux Iptables Firewall Modification

Description

The following analytic detects suspicious command-line activity that modifies the iptables firewall settings on a Linux machine. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on specific command patterns that alter firewall rules to accept traffic on certain TCP ports. This activity is significant as it can indicate malware, such as CyclopsBlink, modifying firewall settings to allow communication with a Command and Control (C2) server. If confirmed malicious, this could enable attackers to maintain persistent access and exfiltrate data, posing a severe security risk.

Detection logic


| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime
from datamodel=Endpoint.Processes where

Processes.process = "*iptables *"
Processes.process = "* --dport *"
Processes.process = "* ACCEPT*"
Processes.process = "*&>/dev/null*"
Processes.process = "* tcp *"
NOT Processes.parent_process_path IN("/bin/*", "/lib/*", "/usr/bin/*", "/sbin/*")

by Processes.action Processes.dest Processes.original_file_name Processes.parent_process
   Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id
   Processes.parent_process_name Processes.parent_process_path Processes.process
   Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id
   Processes.process_integrity_level Processes.process_name Processes.process_path
   Processes.user Processes.user_id Processes.vendor_product


| 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`