AWS MSK - Internal Brokers communication

Question

I am using AWS MSK for our production workload and we have been noticing some not very clear log messages in cloudwatch. The messages are about the internal communication between brokers (more on cluster setup later):

[2022-05-14 06:50:17,171] INFO [SocketServer brokerId=2] Failed authentication with ec2-18-185-175-128.eu-central-1.compute.amazonaws.com/18.185.175.128 ([97fe8ff0-ee38-46c5-ae21-1545fd571224]: Access denied) (org.apache.kafka.common.network.Selector)

Our logs are cluttered with these recurring messages. The logs can be found on all three brokers, all referencing the brokerId=2, as per the message above. I am assuming the instance referenced is one of the MSK brokers.

Whilst the logs are at INFO level and the cluster seems to work fine, I'd like to understand if anyone had to face these sorts of output messages before?

The MSK config is the following:

• 3 brokers over 3 availability zones
• encryption in transit,client_broker = TLS, encryption in cluster
• client_authentication sasl I am
• cluster properties: auto.create.topics.enable = true, default.replication.factor = 3, num.partitions = 3, delete.topic.enable = true, min.insync.replicas = 2, log.retention.hours = 168, compression.type = gzip
• kafka version: 2.7.0

I would be interested to know how to get rid of this log message and if this should be a matter of worry.

Thanks, Alessio