Securing remote connections Post: 302357322

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Operating Systems Linux Securing remote connections Post 302357322 by AlbertGM on Tuesday 29th of September 2009 10:47:48 AM

09-29-2009

Registered User

Securing remote connections

Hi all,

I have a couple of questions I've been searching on internet but I didn't find a suitable solution. The aim is that I'd like to access to my home Linux (an 8.04 Ubuntu) from outside. I already achieved with ssh, but I'd like to secure as much as I can. These are questions:

The account I use to login is a sudoer user. So, I want to connect with an unprivileged user, and then, only if I need, reconnect with that user inside my linux. I'd like to disable that account (root is always disabled) from remote connections. How can I do that? or Where can I find some information to disable that account from remote connections?
One of places I'd like to connect is from office, which has a proxy to connect to a computer out of LAN. Almost all ports are disabled. I'd like to know a way to find out which ports are open, to open in my own home the right one (a port also open in office proxy). I thought using "nmap" or "nc" to my own Linux, but it also has almost all ports closed. So connection is not possible unless I open all ports in my router, which is quite dangerous. Using nc or nmap I won't be able to know if a 'connection refused' is because my router has a certain port closed or because port in office proxy is close.
For example I opened port 443 in my router which redirects to port 22 to my linux. I used this port, because I guessed HTTPS port was available in office proxy. I got right. However, this port is very used and I don't like to leave that port open at home.

Because of my english I don't know if my explanation is good enough, sorry Smilie

Any help will be very appreciate.

Thanks

AlbertGM

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LEARN ABOUT DEBIAN

multinet

MULTINET(8)						      System Manager's Manual						       MULTINET(8)

NAME

       multinet - Connect to a Multinet* DECnet over IP server

SYNOPSIS

       multinet [options] <local-decnet-addr> <remote-host>

DESCRIPTION

       This  utility  creates a tapX device and copies all the DECnet packets from that over IP to a remote Multinet* server. It provides a way to
       connect a Linux box to a remote VMS machine over an IP-only network. Using Linux routing it should be possible to connect  DECnet  networks
       over the internet using this technique.
       local-decnet-addr DECnet node address of the tapX interface. This need not be the same as the address used on other interfaces but it might
       be less confusing if it is.
       remote-host IP address or host name of the remote Multinet server. If you send a HUP signal to the process it will lookup this name  again,
       so you don't need to restart the server if the remote node changes its IP address.

       *Multinet is a product, and probably a trademark, of Process Software.
	      http://www.process.com and is available free for hobbyist use.
	      The protocol used here was reverse engineered by Mark Berryman and Christine Caulfield.

OPTIONS

       -v     Be verbose and dump packet contents to stderr

       -1     Advertise as a level 1 router

       -2     Advertise as a level 2 router (default)

       -D     Make  the tapX device into the default DECnet device. This will force all traffic to non-local nodes down the Multinet link.  IMPOR-
	      TANT: Due to a kernel bug you should not use this option unless you are using a Linux kernel version 2.6.17 or later.

       -p priority
	      Router priority. Default is 64

       -P port
	      Port to talk to Multinet on (default is 700). Ony change this if you know the Multinet server is listening on a different port

       -m MTU Maximum size of packets. (default 576)

       -t secs
	      Timeout for IP connections. If no traffic is seen on the IP connection after this time then the daemon will attempt to restart it.

       -H hello timer
	      How often HELLO messages are sent (default 60) in seconds.

EXAMPLES

	 multinet -1 -D 3.2 zarqon.tykepenguin.com

SEE ALSO

       dnroute(8), ip(8)

DECnet utilities						   March 30 2006						       MULTINET(8)