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 CENTOS

chfn

CHFN(1) 							   User Commands							   CHFN(1)

NAME

       chfn - change your finger information

SYNOPSIS

       chfn [-f full-name] [-o office] ,RB [ -p office-phone] [-h home-phone] -u] [-v] [username]

DESCRIPTION

       chfn  is  used  to change your finger information.  This information is stored in the /etc/passwd file, and is displayed by the finger pro-
       gram.  The Linux finger command will display four pieces of information that can be changed by chfn: your real name,  your  work  room  and
       phone, and your home phone.

       chfn is used to change local entries only. Use ypchfn, lchfn or any other implementation for non-local entries.

   COMMAND LINE
       Any  of	the  four pieces of information can be specified on the command line.  If no information is given on the command line, chfn enters
       interactive mode.

   INTERACTIVE MODE
       In interactive mode, chfn will prompt for each field.  At a prompt, you can enter the new information, or just press return  to	leave  the
       field unchanged.  Enter the keyword "none" to make the field blank.

OPTIONS

       -f, --full-name full-name
	      Specify your real name.

       -o, --office office
	      Specify your office room number.

       -p, --office-phone office-phone
	      Specify your office phone number.

       -h, --home-phone home-phone
	      Specify your home phone number.

       -u, --help
	      Print a usage message and exit.

       -v, --version
	      Print version information and exit.

EXIT STATUS

       Returns 0 if operation was successful, 1 if operation failed or command syntax was not valid.

SEE ALSO

       finger(1), passwd(5)

AUTHOR

       Salvatore Valente <svalente@mit.edu>

AVAILABILITY

       The chfn command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux							     July 2009								   CHFN(1)