ec2 instance is communicating with a remote host on an unusual server port

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Hi, AWS Guardduty is reporting: "ec2 instance is communicating with a remote host on an unusual server port 43582" from and EC2 instance that does not exist. We have autoscaling group that terminates and recreates instances. What could be the real issue?

Many thanks in advance

asked 21 days ago31 views
2 Answers
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The GuardDuty finding contains the Instance-Id. Use this to search AWS Config to gain information about the instance. You can also find API calls involving this instance in CloudTrail.

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EXPERT
kentrad
answered 21 days ago
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The Finding shared resembles to Finding type "Behavior:EC2/NetworkPortUnusual", which informs that a listed EC2 instance in your AWS environment is behaving in a way that deviates from the established baseline. This EC2 instance has no prior history of communications on this remote port.

As in your case, this finding is reported for an EC2 instance that was spin up by auto-scaling, hence I would recommend you to kindly investigate internally and check for what purpose "43582" port is used by those EC2 instances. When troubleshooting unknown open ports, it is useful to find exactly what services/processes are listening to them.

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SUPPORT ENGINEER
Varun
answered 20 days ago

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