Check your EC2 security groups for inbound rules that allow unrestricted access (i.e. 0.0.0.0/0 or ::/0) to TCP port 135 and restrict access to only those IP addresses that require it in order to implement the principle of least privilege and reduce the possibility of a breach. Remote Procedure Call (RPC) port 135 is used for client/server communication by Microsoft Message Queuing (MSMQ): https://goo.gl/GycDGi as well as other Microsoft Windows/Windows Server software.
Allowing unrestricted RPC access can increase opportunities for malicious activity such as hacking (backdoor command shell), denial-of-service (DoS) attacks and loss of data.
To determine if your EC2 security groups allow unrestricted RPC access, perform the following:
To update your security groups inbound/ingress configuration in order to restrict RPC access to specific entities (IP addresses, IP ranges and security groups), perform the following: