Re: How did they get behind my NAT?

On Oct 11, 6:25 am, Leythos <v...@xxxxxxxxxxx> wrote:

- I am running an ADSL router, "Xavi" brand, "7028r" model, and it
seems to run a "GlobespanVirata" chipset. This was provided to me by
my previous ADSL provider, Telefonica Spain.

Not having experience with that router, I can't be sure what limits it
has or what quality of NAT and forwarding it has. The key thing is that
the device does not provide a PUBLIC IP inside the LAN area and that you
have control over what is forwarded inbound.

It does not.


I've seen a number of DSL routers that are PPPOE (no experience with oA)
that use NAT to 1 IP, but they forward ALL ports inbound to that IP - so
the users might as well be on a public IP.


regardless of the inbound transport type (PPPoE, PPPoA, RFC1483, etc),
most NAT router devices (that I have seen) do not by default use a
"default forwarding IP", although it is an option on many. Not this
one, as it turns out.


Double NAT'ing only has an advantage if you have one of those devices
that forwards ALL PORTS to the single internal IP provided by the
device.


ok... and what is the advantage then? The only reason I'm considering
it is because then I can use a regular/standard device like the
linksys wrt54G that is well-known and supported on the internet, turn
on the firewall on that device (which I had to disable on the router I
use now), and keep the services that I need up.


Because if you don't know enough that you have to ask here, it means you
don't know enough to be securely exposed to the internet.

Oh come on - this sounds a lot like "I don't know exactly, but I know
it's a bad idea, so I'm going to make fun of you instead of answering
the question". I understand that exposing a port exposes any service
that listens on that port. I also understand that that then means any
vulnerability in that service then becomes a vulnerability for the
entire server, and potentially (in my case, without DMZ etc) the
entire network. I understand that, and it's a risk I'm OK with. My
question is whether anyone can tell me whether there are any
circumstances under which port forwarding is "bad" in and of itself,
rather than because of any vulnerabilities in the services that it
purposefully exposes.


uTorrent doesn't expose your VNC, but, there is any number of unknowns
where as to what you've done in addition. The issue is that I've not see
anyone that needs to run a file-sharing program on their computer unless
they were pirating files of some type. Yea, not always true, but it's a
good assumption since there are legal means and methods without using
file sharing methods.


OK, now there's a sensible suggestion - you're saying (unless I got it
wrong) that the infection probably had nothing to do with the port
forwarding at all, but rather was because of some something I picked
up while downloading all those pirated "w4r3z" that I keep hidden
under the kitchen sink, and that said malware has escaped detection
either through comporomising my detection tools or because they're
just too specific, not known widespread infections. To be fair, that
is a possibility. I do take more risks than I probably should, I could
well at some point have run something I shouldn't have... but I don't
think so.



No, it's the start of trying to determine what happened while you are
also secure to do it. NAT only blocks inbound, so you could learn if
what's on your machine also phones home or creates a connection to a
remote location to allow control. First thing is block inbound
connections, second is monitor outbound connections or block them
entirely while you look.

Ah, now there's a sensible suggestion, again - running a software
firewall or carefully monitoring all outgoing traffic on the router (a
monster task, i
it's accumulated 20 megs of data in 1 day) would certainly help
identify any unpleasant low-key trojan I may have running.


AVG is crap - I've seen hundreds of computers with AVG compromised. I
use Symantec Corporate software, it's not a resource hog like Norton is
and it's stopped all that I've been exposed to.

If you want to know what AV products to trust, I've always found this
site to have unbiased reviews and test results:

http://www.av-comparatives.org/


Nice to know, thanks!

Here are a few tools that I use and trust:

Always remember - only download files from Trusted Sites.

The following links will take you to vendors sites for Spy Ware / Ad
ware removal tools and also for Antivirus tools. After you install any
of these applications and update them, run them in SAFE MODE to allow
them to properly clean your system.

First, make sure that your Java is updated to the latest version:http://www.java.com/en/download/index.jsp

These sites are for downloading Anti-Malware and Anti-Spyware tools, in
order that I would use them myself:

Dave Lipman's tools:
Download MULTI_AV.EXE from the URL --http://www.pctipp.ch/ds/28400/28470/Multi_AV.exe

AdAwareSE can be found here:http://www.lavasoft.com/products/ad_aware_free.php

SpyBot Search and Destroy can be found here:http://www.safer-networking.org/en/download/index.html


Thanks, never heard of multi-AV

err - how does safe mode help? you mean so I don't have any additional
programs running?

Because many malware can't run in safe mode - it's not just "you having
any additional programs running". In the case of Multi-av, download it,
run it in normal mode to get the updates, but don't run the scans, then
reboot in safe mode, run it again, since safe mode disables the network,
you've already downloaded them, now run the scans, full drive, run each
of the 4 scanners and run them until nothing is found.


Fair enough, I didn't realize the idea was to more thoroughly scan for
malware, but with the suggestions above I think I'm well equipped to
do that :)



I'm well aware of torrent software, but I don't use it either and never
have a problem getting distro's downloaded. I don't subject my networks
to unknowns.

ok, but calling the entire family of bittorrent programs a general
"unknown" is exaggerating a little, no? The protocol is well-specified
and well-understood, there are the same security measures built in as
for a direct download from a distributor via HTTP or FTP (i.e MD5
hash). If you're referring specifically to uTorrent, fair enough. Not
open-source, already had one known vulnerability - I'd say it's more
risky than I planned.


I also don't download apps I've not paid for or music or anything that
is questionable - not saying you do, as you've side stepped that issue -
but the quickest way to get compromised is to start downloading pirate
wares.

Yep, that's fair.


5) Put your website on a proper web server, one protected by a real
firewall and on a locked down OS following the OS Vendors FULL
SUGGESTIONS ON HOW TO SECURE IT.

ok, so what you're saying is that there is no way to safely run a
simple website without paying out either professional hosting fees or
buying all the equipment that hosting vendors require. A safe, but
uninspiring, answer.

No, what I'm saying is that there is little chance that a non-OS guru,
that a non-technical type, is going to run a website without being
compromised or exploited - notice why you are here.

Yep, but that's how you learn. I'm a little bit irked by your
condescending tone, but I really do appreciate the time and help -
while I have worked with professional windows-based webserver
development and hosting for several years and have a pretty good idea
of "best practices" are at a corporate level, I'm trying to work on a
shoe-string budget here, get a taste for doing things for free or
cheap. As I get burned, I'm trying to understand exactly why and how.



UPnP is disabled, but I would love to understand what the problem /
risk with port forwarding is - can you provide any information, links,
resources to help me understand?

IF you allow anyone in you risk being connected too, simple enough to
understand.

But more than a little simplistic, no? The ONLY argument against port-
forwarding that I have seen from you so far, and that I was well
aware of before, is that it limits the security of your server, and in
my case network, to the security of the service running on the
forwarded port. On the other thread (sorry about the messed up cross-
post, like I said I am new here), someone suggested that there are
ways and means to gain access to a port OTHER than the one being
forwarded - but if I understand correctly that argument applies
equally if you don't forward ports at all!



If you run a website then you really need to step back and start
learning about security and how to setup a DMZ and how to lock down your
services, BEFORE YOU PUT THEM ONLINE.

Well, I was pretty sure I had :)

Which is why I'm trying to understand where I went wrong. As you've
noted, I have probably not searched extensively enough for malware - I
will keep at it. Other than that, I run an updated version of Apache,
there are no known vulnerabilities for other services I expose,
uTorrent seems the most risky, and the jury's still out on what
actually caused the problem:
- malware that I somehow acquired?
- unknown uTorrent vulnerability?
- misunderstanding of how NAT works, leading to attacker's ability to
access a port that was NOT forwarded?



Port Forwarding - means you are allowing the WORLD ACCESS TO THE PC YOU
ARE PORT FORWARDING TO, FOR THAT PORT/SERIES OF PORTS. If you don't have
the service answering that port(s) secured then you've exposed your
network.

Yes, that's pretty obvious. But that's not a problem with port
forwarding, it's a problem with the services you are exposing.
Obviously if they are not secure, and they are public, nothing is
secure.

Thanks again,
Tao

.

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