How to Find AWS EC2 Security Groups Allowing All Inbound Traffic on Default Telnet Ports
If security groups are not properly configured, the attack surface is increased.
info
This security check is part of the CIS Amazon Web Services Benchmarks and is rated severity high.
Prerequisites
This guide assumes that you have already installed and configured Fix Inventory to collect your AWS resources.
Directions
-
Execute the following
search
command in Fix Inventory Shell:> search is(aws_ec2_security_group) and group_ip_permissions[*].{(ip_protocol=-1 or (from_port>=23 and to_port<=23 and ip_protocol=tcp)) and (ip_ranges[*].cidr_ip="0.0.0.0/0" or ipv6_ranges[*].cidr_ipv6="::/0")}
kind=aws_ec2_security_group, ..., region=fixinventory-poweruser
kind=aws_ec2_security_group, ..., account=poweruser-team -
Pipe the
search
command into thedump
command:> search is(aws_ec2_security_group) and group_ip_permissions[*].{(ip_protocol=-1 or (from_port>=23 and to_port<=23 and ip_protocol=tcp)) and (ip_ranges[*].cidr_ip="0.0.0.0/0" or ipv6_ranges[*].cidr_ipv6="::/0")} | dump
reported:
id: /aws/ec2/123
name: some-name
ctime: '2022-12-05T22:53:14Z'
kind: aws_ec2_security_group
age: 2mo28dThe command output will list the details of all non-compliant
aws_ec2_security_group
resources.
Remediation
- Apply Zero Trust approach.
- Implement a process to scan and remediate unrestricted or overly permissive network ACLs.
- Recommended best practices is to narrow the definition for the minimum ports required.
note
Please refer to the AWS EC2 documentation for details.