Unrestricted Inbound Access on Uncommon Ports

01 Sign in to the AWS Management Console.

02 Navigate to EC2 dashboard at https://console.aws.amazon.com/ec2/.

03 In the left navigation panel, under NETWORK & SECURITY section, choose Security Groups.

04 Select the EC2 security group that you want to examine.

05 Select the Inbound tab from the dashboard bottom panel.

06 Verify the value available in the Source column for any inbound/ingress rules with uncommon ports. If one or more rules have the source set to 0.0.0.0/0 or ::/0 (Anywhere), the selected security group allows unrestricted traffic to uncommon ports, therefore the access to the EC2 instance(s) associated with the security group is not restricted.

07 Repeat steps no. 4 – 6 to verify the rest of the EC2 security groups available in the current region.

08 Change the AWS region from the navigation bar and repeat the audit process for other regions.

01 Run describe-security-groups command (OSX/Linux/UNIX) using the necessary filters to expose the security groups with inbound/ingress rules that allow traffic from all addresses (0.0.0.0/0 or ::/0), available in the selected region:

aws ec2 describe-security-groups
	--region us-east-1
	--filters Name=ip-permission.cidr,Values='0.0.0.0/0'
	--query 'SecurityGroups[*].GroupId'

aws ec2 describe-security-groups
	--region us-east-1
	--filters Name=ip-permission.ipv6-cidr,Values='::/0'
	--query 'SecurityGroups[*].GroupId'

02 The command output should return an array with the requested information. If the command does not return any output, there are no EC2 security groups that allow unrestricted access (0.0.0.0/0 or ::/0), otherwise it should return the ID(s) of the security group(s) that match filter criteria, as shown in the following example:

[
    "sg-48016733",
    "sg-5365d728",
    "sg-960167ed"

]

03 Run again describe-security-groups command (OSX/Linux/UNIX) using custom filtering to list all the inbound rules defined for the selected security group:

aws ec2 describe-security-groups
	--region us-east-1
	--group-ids sg-5365d728
	--query 'SecurityGroups[*].IpPermissions[]'

04 The command output should return the requested inbound rules metadata:

[
    {
        "PrefixListIds": [],
        "FromPort": 8040,
        "IpRanges": [
            {
                "CidrIp": "0.0.0.0/0"
            }
        ],
        "ToPort": 8040,
        "IpProtocol": "tcp",
        "UserIdGroupPairs": []
    },

    ...

    {
        "PrefixListIds": [],
        "FromPort": 115,
        "IpRanges": [
            {
                "CidrIp": "0.0.0.0/0"
            }
        ],
        "ToPort": 155,
        "IpProtocol": "tcp",
        "UserIdGroupPairs": []
    }

]

05 Repeat step no. 3 and 4 to verify the inbound rules of the remaining EC2 security groups available in the current region.

06 Repeat steps no. 1 – 4 to perform the audit process for other AWS regions.

01 Sign in to the AWS Management Console.

02 Navigate to EC2 dashboard at https://console.aws.amazon.com/ec2/.

03 In the navigation panel, under NETWORK & SECURITY section, choose Security Groups.

04 Select the appropriate security group.

05 Select the Inbound tab from the dashboard bottom panel and click the Edit button.

06 In the Edit inbound rules dialog box, change the traffic Source for any inbound rules that allow unrestricted access through TCP/UDP uncommon ports by performing one of the following actions:

1. Select My IP from the Source dropdown list to allow inbound traffic only from your machine (from your IP address).
2. Select Custom from the Source dropdown list and enter one of the following options based on your access requirements:
   • The static IP/Elastic IP address of the permitted host with the suffix set to /32, e.g. 50.164.53.108/32.
   • The IP address range of the permitted hosts in CIDR notation, for example 50.164.53.108/24.
   • The name or ID of another security group available in the same AWS region.

07 Click Save to apply the changes.

08 Repeat steps no. 4 – 7 to update other EC2 security groups that allow unrestricted inbound access.

09 Change the AWS region from the navigation bar and repeat the process for other regions.

01 First, run revoke-security-group-ingress command (OSX/Linux/UNIX) to remove the inbound rule(s) that allow unrestricted access through uncommon ports, from the selected EC2 security group. Set the --protocol parameter value to tcp or udp based on your needs (the command does not return an output):

aws ec2 revoke-security-group-ingress
	--region us-east-1
	--group-id sg-5365d728
	--protocol tcp
	--port 8040
	--cidr 0.0.0.0/0

02 Run authorize-security-group-ingress command (OSX/Linux/UNIX) to add the ingress rules removed at the previous step with a different set of parameters in order to restrict inbound access to specific entities. To add custom inbound/ingress rules to the selected security group, use one of the following options (the command does not produce an output):

1. Add an inbound rule that allows access only to the specified static IP/Elastic IP address of the permitted host using uncommon port 8040:
   aws ec2 authorize-security-group-ingress
   	--region us-east-1
   	--group-id sg-5365d728
   	--protocol tcp
   	--port 8040
   	--cidr 50.164.53.108/32
   

2. Add an inbound rule that allows access only to the IP address range of the permitted hosts using uncommon port 8040:
   aws ec2 authorize-security-group-ingress
   	--region us-east-1
   	--group-id sg-5365d728
   	--protocol tcp
   	--port 8040
   	--cidr 50.164.53.108/24
   

3. Add an inbound rule that allows access only to another EC2 security group in the same AWS region using uncommon port 8040:
   aws ec2 authorize-security-group-ingress
   	--region us-east-1
   	--group-id sg-5365d728
   	--protocol tcp
   	--port 8040
   	--source-group MyWebAppSecurityGroup
   

4. Change the --port parameter value based on your requirements and repeat steps a – c to add the necessary inbound rule(s) that you removed at step no. 1.

03 Repeat step no. 1 and 2 to update other EC2 security groups that allow unrestricted inbound access using AWS CLI.

04 Repeat steps no. 1 - 3 to implement the entire process for other AWS regions.