Apache mod_security is a firewall module to prevent against SQL Injection, cross site scripting, bad user agents, and a lot of other exploits.
Depends on the Amazon Linux AMI version you may have to issue one of the below commands on a trial & error basis.
sudo yum install mod24_security.x86_64
The Amazon Linux AMI is a Linux image provided by Amazon Web Services (AWS) for use on Amazon EC2. It is designed to provide a stable, secure, and high performance execution environment for applications running on Amazon EC2.