I would agree that there is something to be said for learning to batten
down your linux boxen. However, keeping things  behind a firewall is
just good practice. Yes, it may give one a false sense of security, but
it also gives one a safe place to learn and grow; i.e. behind the
firewall. With a firewall, you can limit the ports available from the
outside straight away. True you can do that with a Linux box from the
outset, but there may be things you want to do in the meantime that
require those services.  I think in general, having a firewall in place 
is always a plus and having more of them limits the number of hacked
boxes and launching pads for other exploits. No it's not a cure-all, as
so many have pointed out. But I'd still recommend everyone having one.

<<JAV>>

On Thu, 2003-02-13 at 15:18, Bill Anderson wrote:
> On Thu, 2003-02-13 at 12:01, Kent Borg wrote:
> > On Thu, Feb 13, 2003 at 11:58:58AM -0600, Dave Ihnat wrote:
> > > On Thu, Feb 13, 2003 at 10:02:54AM -0500, Kent Borg wrote:
> > > > On Thu, Feb 13, 2003 at 07:56:23AM -0600, Dave Ihnat wrote:
> > > > > We all urgently push you to implement a firewall...any firewall...
> > > > 
> > > > No we don't (with or without smilies), I do not advise a firewall
> > > > unless you are trying to protect some MS Windows garbage and that is a
> > > > losing battle you are better off not trying to fight.  
> > > > <<Rest of message elided>>
> > > 
> > > With all due respect, not only is that a very misguided attitude, it's a
> > > dangerous one to promulgate.
> > 
> > First, a point of order: if you are sincere about the "with all due
> > respect"-part, then don't suggest that I am a cracker.
> > 
> > > Read what you said
> > 
> > I wrote a short post describing how to make and keep a Red Hat system
> > secure.  I glossed over some details, but I still think it was pretty
> > good, and damn specific, given how short it was.
> 
> My problem with the method you propose is that it requires you to be
> able to determine vulnerabilities before they happen.Say you are
> attending a Linux Expo, or some other event that takes you away from
> your machine(s) for the day. That morning a vulnerability is announced
> that has an exploit. Your machine(s) is(are) vulnerable until you update
> it. If it is a network exploitable vulnerability.
> 
> Specific? Well, do you like to print, and run lpd? it's had problems in
> the past.
> 
> 
> > You assert that it won't work.  OK, be specific.  Reread what I
> > posted.  Assume that such a RH 7.0 system has been on the internet,
> > maintained as I described, without a firewall, for the last two years.
> > Tell me how it got rooted during time.  Be specific.
> 
> It's maintainer was at work, and it was a home machine running the
> vulnerable LPRng and did not update the machine until they were a) aware
> of the problem, and b) able to update to a fixed version. For example:
> http://rhn.redhat.com/errata/RHSA-2002-089.html
> 
> 
> An example clipped from an incident report:
> --------------------------
> Port 515 on our network was scanned from uiowa.edu over the weekend. 
> Here's some information on the LPRng exploits attempted against several 
> RedHat Linus 7.x hosts. The intruder attempts to create a file called 
> /dev/whoa/reg. It looks like they intend for reg to open port 8282 with 
> root privileges. They then edit xinetd.conf file and restart xinetd to 
> open the port. Evidence of these changes was cleared from compromised 
> hosts once the intruder installed his kit. A password protected guest 
> account with a GID of 0 was created on one compromised host. The 
> following files were also changed: du, find, ls, netstat, passwd, ping, 
> psr, and su. 
> -----------------
> 
> Running X-Windows on said system? Uh-oh, there's another potential
> problem (especially if xdm was enabled).
> 
> Ascii-only email/web? Pine, Mutt (CAN-2002-0001) and lynx have had their
> problems w/security as well. Pam has had it's problems, which in at
> least one case allowed users to get another's access credentials.
> 
> The problem with your method is that it does not "think like a cracker".
> It "thinks" like someone who believes they are faster and superior to
> the cracking ability. IMO, that is as bad as relying solely on a
> firewall. Security is not an item, it is a process and mindset. 
> 
> While it is true for all systems that there is a period of vulnerability
> between the finding/reporting of the vulnerability/exploit and the
> updating of the system, by not using a firewall, you pile more openings
> on top of ones that affect, for example, bind or mod_ssl. There are
> exploits that allow the remote attacker to get a non-root local access.
> Combine this with a local-root exploit and bam, You have a problem.
> 
> IMO, this is as dangerous as "we have a firewall, who cares?".
> 
> -- 
> Bill Anderson
> RHCE #807302597505773
> [EMAIL PROTECTED]
> 
> 
> 
> 
> 
> -- 
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