Security is one of the most critical areas of using the cloud. It's important to get it right because good security practices reinforce themselves, leading to a virtuous cycle of capabilities and control.
There are many tools and AWS services to ensure that your cloud-based infrastructure is as secure—if not more secure—than your own resources.
AWS IAM is the backbone of security in AWS. It provides incredibly granular levels of permissions to allow (and deny) specific users access to your resources.