How to deny all outbound traffic from an AWS EC2 instance using a Security Group?

Question

I'm working with AWS and I want to set a Security Group egress rule that will block all outbound traffic. How can I do this using CloudFormation?

Answer 1

There is no option for denying traffic for security groups, it's just that you can leave them empty.

So you can define a rule that doesn't do anything so that the default rule is not applied.

You can take reference from the below:

"InstanceSecurityGroup": {

  "Type": "AWS::EC2::SecurityGroup",

  "Properties": {

    "VpcId": {

      "Ref": "VPC"

    },

    "SecurityGroupIngress": [

      {

        "IpProtocol": "tcp",

        "FromPort": "80",

        "ToPort": "80",

        "CidrIp": "0.0.0.0/0"

      }

    ],

    "SecurityGroupEgress": [

      {

        "IpProtocol": "tcp",

        "FromPort": "1",

        "ToPort": "1",

        "CidrIp": "0.0.0.0/32"

      }

    ]

  }

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