Securing a Linux Server

#1

Post by shawndumas » Sat, Sep 14, 2013, 4:01 AM UTC

Re: Securing a Linux Server

#2

Post by ChuckMcM » Sat, Sep 14, 2013, 5:21 AM UTC

This is a good start, netstat -an to see what ports are open, to shut down things that open ports. Turn of xinetd if it is on, etc. There was a much more complete best practices document that came through here earlier.

Re: Securing a Linux Server

#3

Post by lloeki » Sat, Sep 14, 2013, 5:48 AM UTC

Important caveat: fail2ban does not work for IPv6 connections yet (there are patches floating around though)

Re: Securing a Linux Server

#4

Post by chrsstrm » Sat, Sep 14, 2013, 5:48 AM UTC

The first time I locked down a server I found iptables to be a little intimidating. If you're on Ubuntu then ufw is extremely easy to use - it's just a front end for iptables.

https://help.ubuntu.com/community/UFW

Re: Securing a Linux Server

#5

Post by stollercyrus » Sat, Sep 14, 2013, 5:51 AM UTC

ChuckMcM wrote: post #2

This is a good start, netstat -an to see what ports are open, to shut down things that open ports. Turn of xinetd if it is on, etc. There was a much more complete best practices document that came through here earlier.

Which one are you referring to?

Re: Securing a Linux Server

#6

Post by jonahx » Sat, Sep 14, 2013, 6:09 AM UTC

lloeki wrote: post #3

Important caveat: fail2ban does not work for IPv6 connections yet (there are patches floating around though)

ty, i didn't know that was the case. are there other alternatives?

Re: Securing a Linux Server

#7

Post by aristidb » Sat, Sep 14, 2013, 6:09 AM UTC

ChuckMcM wrote: post #2

This is a good start, netstat -an to see what ports are open, to shut down things that open ports. Turn of xinetd if it is on, etc. There was a much more complete best practices document that came through here earlier.

netstat -an shows a lot of stuff. I think here all you need is

netstat -ntul

(Thanks "child", I did indeed initially not have the -u there. You should.)

Re: Securing a Linux Server

#8

Post by zerop » Sat, Sep 14, 2013, 6:16 AM UTC

Very useful for any Linode user.. Compare to AWS, I find it hard to manage security on Linode boxes.. Need concept of security groups like AWS configurable and manageable from UI..

Re: Securing a Linux Server

#9

Post by e12e » Sat, Sep 14, 2013, 6:21 AM UTC

aristidb wrote: post #7

ChuckMcM wrote: post #2

This is a good start, netstat -an to see what ports are open, to shut down things that open ports. Turn of xinetd if it is on, etc. There was a much more complete best practices document that came through here earlier.

netstat -an shows a lot of stuff. I think here all you need is netstat -ntul (Thanks "child", I did indeed initially not have the -u there. You should.)

Better yet, netstat -nltu (--numeric --listening --tcp --udp). You probably want to shut down anything unwanted that binds an udp-socket too.

Re: Securing a Linux Server

#10

Post by ruttiger » Sat, Sep 14, 2013, 6:28 AM UTC

I made the mistake of accidentally setting the firewall too strict on a remote server, killing my ability to SSH. A neat little trick I found was to setup a scheduled task to kill the firewall in 5 minutes, and then restart it. If it's too restrictive and locks you out, wait 5 minutes. If you did it right, then kill the scheduled task.