security risk in port forwarding?

[Fullmetal Chocobo]

I just built a linux box (Ubuntu Server 7.10), and I have been experimenting a lot with it recently. I now have a SFTP server configured so that I can access the terminal remotely, so I have port 22 & 21 forwarded to the linux box. I also have port 80 forwarded to the machine and have a testing page up (just text that reads "This is just a test."). Also, I used DynDNS so I don't have to type in the IP.

Is this safe to do? I believe it is, but I am messing around with this and just learing, so I want to make sure there are no major security risks in doing this.

The machines are behind two firewalls, and they are from different manufacturers. I'm going through the process now to actively encrypt personal data & documents using a 3rd party program.

 

[spidey07]

It's only a risk in that those services are now vulnerable to any exploits and brute force password attacks. Those are very popular for bots and automated scanning.

Keep your stuff up to date/patched (os and services) and use strong passwords and you should be fine.

 

[QuixoticOne]

It's as safe as the applications listening to ports 20,21,80 are.

It isn't too uncommon for there to be vulnerabilities like buffer overflows that can compromise the security of programs like a web server or SFTP server.

It is also possible to use the fact that the ports are forwarded through your firewall to help get the packets onto your local LAN in which case they could take advantage of some weakness of the network protocols in your router/firewall or forward target PC to do unexpected things or to help probe other aspects of your network.

It may also be possible for someone to try to hack your passwords if they try to authenticate to the web server or SFTP server and those servers are able to use your main OS accounts and credentials for login.

I seem to remember having a somewhat negative security impression of SFTP at the time I looked into it in the past. I think mainly that was because it didn't seem to be very certain it was free of buffer overflow type vulnerabilities, that it seemed hard to totally sandbox its user account login and filesystem access, and that it used security protocol transports that themselves had had some associated weaknesses / exploits in recent years.

I think you're probably a little safer using scp / ssh over SFTP just because I think ssh/scp are probably more mature / stable / widely used / widely audited that they may be a bit more robust / reliable / secure.

As for a web server, well they often have somewhat insidious problems even if you think you've locked down what file(s) and directories they serve. If you use a well patched / fairly secure server code, though, it should probably be pretty good as long as you don't fail to secure it properly in your administration.

If you can lock the whole thing down somehow like by using firewall rules to restrict access to given trusted IP / MAC addresses, or even by using a VPN / IPSEC type access exclusively, you'll probably be a bit more secure.

If you ran the services in a VM that'd probably give you a little more security insulation too.