IPTABLES - Unexpected traffic - EC2 - Should I configure IPTABLES on instance command line?

Question

Hi there. I'm migrating on-premise server running MySQL to a new EC2 instance (Amazon Linux 2). I'm trying to move IPTABLES configuration to EC2 as well, but I see unexpected traffic being blocked by IPTABLES. I'm starting to suspect that AWS ping the EC2 instance on time basis for monitoring and thus has being causing these unexpected traffic. Is that right ?

I know firewall rules can be configure when lunching EC2 instance, but I'd like to know whether is a good practice to define IPTABLES on instance command lines. Does IPTABLES configuration compromises AWS to monitor instances?

Should I configure IPTABLES on EC2 instances?

Thanks,
Marcelo Maciel

Answer

Hi Shibata. Thanks for your reply!

Security Groups is not a bad option, but it can't replace IPTABLES in full. It's only possible to create complex rules (using states and expressions) with IPTABLES.

It's not clear to me whether IPTABLES rules prevent any AWS functionaly to work

Answer

So far, I think I should combine both IPTABLES and Security Groups.

For example, on Security Groups I would allow traffic on 22 and 3306 ports. On IPTABLES I would allow all traffic, but drop those with bad flags.

In other words, on Security Groups I could configure what is allowed and on IPTABLES I could configure how its allowed

Answer

I prefer to use Security Groups to protect EC2 from external communication.

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-security-groups.html

I can't find the documentation, but EC2 stats checks should work fine even if all packets are droped using iptables.
However, I don't know about other services.

IPTABLES - Unexpected traffic - EC2 - Should I configure IPTABLES on instance command line?

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