For AWS environments it is a good idea to keep track of allocated IP addresses and DNS Route53 reservations.
If you whitelist IPs on the ALB or ELB regularly audit those IP addresses.
It is easy for an IP address to get abandoned and reallocated to third party that would now have access to your systems.
The same for DNS entries. If you retire a service but not remove the DNS from Route53, a third party could take over that IP and now your DNS is sent to a third party service. This is a common tactic for malicious and scam sites to use your company name to drive traffic to their site.
Regular audits and system offboarding processes will help take care of these issues and save you many headaches.
