AWS free-tier instance port discrepancy from Security Group specifications

Question

My Ubuntu Server 11.04 free-tier instance security group opens SSH, HTTP, HTTPS to the public web and nothing else (not even the inter-group TCP/UDP/ICMP ports enabled by the default sec group).

But when I Nmap my server's public dns, it shows HTTP & HTTPS closed, with ftp (21), rtsp (554), and realserver (7070) all open. This would, of course, explain why I can't view the website I'm running on that instance, so I need to fix it.

This is a cross-post from the AWS EC2 forum, but since I've got no replies yet, I'm hoping for better luck here.

my SecGroup (no other rules for UDP or ICMP):

TCP 
Port (Service)  Source  Action
22 (SSH)    0.0.0.0/0   Delete
80 (HTTP)   0.0.0.0/0   Delete
443 (HTTPS) 0.0.0.0/0   Delete

Nmap:

kurtosis@kurtosis-laptop:~/bin/AWS$ nmap ec2-184-73-70-26.compute-1.amazonaws.com
Starting Nmap 5.00 ( http://nmap.org ) at 2011-06-14 23:27 PDT
Interesting ports on ec2-184-73-70-26.compute-1.amazonaws.com (184.73.70.26):
Not shown: 994 filtered ports
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
80/tcp closed http
443/tcp closed https
554/tcp open rtsp
7070/tcp open realserver

Nmap done: 1 IP address (1 host up) scanned in 8.52 seconds

Why are http and https closed when my security group specifies they should be open, and why is ftp, rtsp, and realserver open when my security group does not include them at all? Anyone know why the discrepancy?

Answer 1

Are you sure your instance is a member of the security group you're modifying? In the EC2 Console you can see this by clicking on the Instance, it'll list the security groups it's a member of as "sg-12345".

Alternatively it may be an issue with just that instance - try terminating that instance and starting a new one to see if the problem persists.