AWS EC2 instance has SMTP open despite not enabling it in security group

1
votes

Observing a strange behaviour on Amazon EC2 instance.

I have a Ubuntu in AWS EC2 instance running. Created a security group to enable ssh/http/https.

when i do nmap to the VM from external to AWS , i see that port 25 is open and i can telnet to it . But when I login to the same EC2 instance and do nmap (on localhost or internal IP or external IP) the port 25 is not open ! nor any sendmail service is running on the VM at all !

i have no other instances running

1
amazon-web-servicesamazon-ec2smtp
Are you sure you are telneting and logging in to same instance? - Dusan Bajic
"port 25 is open and i can telnet to it" Does the SMTP greeting banner provide any identifying information? The scenario described seems impossible. - Michael - sqlbot
@DusanBajic yes because i dont have any other instances ! - sashank
@Michael-sqlbot nope no banner, seems strange to me too - sashank
You might be telneting to someone else's SMTP server (are you testing from some corporate network?) - Dusan Bajic

1 Answers

0
votes

From which server are you telneting? Is it from within the same EC2 instance OR from another instance in same VPC in AWS iteself OR from outside the AWS/VPC (over internet) ?

Which IP are you using to telnet? The Elastic IP of your EC2 instnace or the private IP of your EC2 Instace?