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Inbound RPC access is restricted

ec2

Classification:

compliance

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Description

Reduce the probability of a breach by checking EC2 security groups for inbound rules that allow unfettered access to TCP port 135 (used by Microsoft Message Queuing (MSMQ) and other Windows software) and restrict access to IP addresses that require this port.

Rationale

Malicious activity, such as backdoor command shell hacking and denial-of-service (DoS) attacks, can occur when permitting unfettered access to this port.

Remediation

Console

Follow the Security group rules docs to learn how to add a security group rule that will restrict access to a specific port.

CLI

  1. Run revoke-security-group-ingress to remove inbound rules that allow unrestricted access to port 135.

    revoke-security-group-ingress.sh

        aws ec2 revoke-security-group-ingress
            --group-name group-name
            --protocol tcp
            --port 135
            --cidr 192.0.2.0/24
        
  2. Run authorize-security-group-ingress to add new inbound rules that restrict port 135 access.

    revoke-security-group-ingress.sh

        aws ec2 authorize-security-group-ingress
            --group-name your-group-name
            --protocol tcp
            --port 135
            --cidr 192.0.2.0/24