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RE: Open All Outbound Ports?

From: Louis Erickson <LErickson () ariba com>
Date: Fri, 15 Nov 2002 10:39:03 -0800
By using a proxy at your NAT gateway, you can allow passive ftp from insidethe firewall to work properly.  You need more than port mapping to do it,but it can be done.  OpenBSD and Linux's firewalls both do thistransparently, I believe, at least for people inside trying to use FTP tothe outside.  It doesn't allow FTP back in, or didn't last time I tried.I will admit that my personal network (nothing to do with Ariba, who'snetwork configuration I don't know, and don't care as long as the things Ineed to do work properly) has all outbound ports open, via NAT.  Incoming isheavily filtered, but once you're in, you can connect to anywhere.  I'm toolazy for myself and the other users of my resources to try and specificallyallow anywhere they might connect to.  (In this case irc, muds, online gamesand such which tend to have ports all over the map as well.)  To help limitthis, I make sure my (very small group of) users is educated about what notto do, and insist upon good virus scanning software.  So far, so good.While I do see the risks inherent with this, I don't know a good way aroundit that will allow people to use all the myriad and unusual pieces ofsoftware they want to use.  There's a risk assessment you have to do, and todecide what you solve through technology, and what you solve through policy.If you can't trust your staff to follow policy, that's a different problemthat no technology will ever be able to solve.I also suspect that there are a lot of networks that allow any outboundconnection from the private LAN, despite the misgivings of their securitystaff.  Again, it's risk management and assessment; yes, it's risky, but notdoing it irritates the other thousand people at the company, or evenprevents them from doing their work successfully - what choice willmanagement make?Sometimes they do choose security; I was at a large computer company where Ihad to work from home; the corporate firewall wouldn't allow me to connectto our customer's sites the ways I needed to, and they wouldn't budge onopening ports.  We also had to use application level FTP and Telnet proxies,and to set the web proxy in our browsers; I don't think they allowed any rawnetwork packets across.  So, I had to work from home, and they covered partof my DSL.  They had decided security was worth that cost in the few caseswhere the employee could really justify it.  I later discovered that thiswas not common to the whole company, and only done at sites where they didwork requiring government classifications; it was quite a shock to travelingemployees that instant messaging didn't work.Other times they don't, and you have to be ready to cope with that.  Makesure they understand it's a decision they're making, and that they may haveto live with the consequences, and do what you have to do.
-----Original Message-----From: Chris Alliey [mailto:calliey () bellatlantic net]Sent: Wednesday, November 13, 2002 8:44 PMTo: Chris Berry; security-basics () securityfocus comSubject: RE: Open All Outbound Ports?I know I don't have all the expertise that a lot of the people on this listprobably have - so PLEASE take it easy on me for responding to this.I too have had a 'network engineering' team make this suggestion, and get itpassed (over my objections).  Even though I brought up a lot of the reasonsalready mentioned (security, DDOS zombies, Kazaa, limewire, ....),executives allowed them to open the ports out -- because they are the'network security experts' in our company.  I never agreed with it, but oneof their reasons to open this was passive FTP.  Their reason was a lot ofthe sites that were visited used Passive FTP, that randomly uses any portabove port 1024.Can anyone comment on this?  This never sat well with me, and I reallydidn't like it when vendors who brought laptops into our environment -discovered this, after only 1 week on site :-(    As a server engineer, I'vehad to deal with the NIMDA and other worms/virii/....  as you can guess,that was a little worrisome.Chris-----Original Message-----From: Chris Berry [mailto:compjma () hotmail com]Sent: Monday, November 11, 2002 4:03 PMTo: security-basics () securityfocus comSubject: Re: Open All Outbound Ports?
From: tony tony <tonytorri () yahoo com>Our firewall group has came to me several times over the
last few >months
wanting my approval to open all of the "OUTBOUND" ports on
our >firewall
facing the internet.
Not a good idea.  One of the most important things during a security breachis to keep the attacker from using your platform as a staging ground.  Bypreventing them from commincating freely, you greatly retard theircapabilities.  For example, a trojan will probably try to "phone home" andif you have blocking set up this will show in your logs.  By opening allyour outbound ports you're just asking to be a DDOS zombie, warez ftpserver, etc.
Their argument is that this would not >significantly reduce
our >securityNot true, just like a military base its important to know what is going outas well as what is coming in.
and it will reduce their time/effort in administration.
Possibly true, although the amount of time it takes to open a set of portscan't be very long.
They claim they get several requests a week to open up out
bound ports >and
the number keeps growing each month.
How can this be true, this would make me highly suspicious, I would want arecord of all the ports they've opened over the last three months and whatprograms/services they opened them for.  I mean unless you guys are goingthrough some kind of major upgrade cycle their should be little or no changein your port list on a monthly basis.
They want to go for the gusto...and >open up all 65,000+
outbound ports.
I am in the security area and they want my agreement/sign
off before >they
do this.  It just does not "feel/smell right" but I am
losing >ground with
my arguments.  What are some good arguments I can use?
Not only would I not sign off on this, I'd launch an investigation intotheir procedures, something definitely doesn't feel right here.  I wouldsuspect that they are allowing traffic that they shouldn't be just becausesomeone asked for it.  Kazaa for example.Chris Berrycompjma () hotmail comSystems AdministratorJM Associates"And here in our server room you can see our Beowolf Cluster of C64's thatkeeps our enterprise on the very cutting edge of technology."_________________________________________________________________The new MSN 8: smart spam protection and 2 months FREE*http://join.msn.com/?page=features/junkmail
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