discuss how to make yourself unpopular with your co-workers.
This is not the sort of advice you read about in Miss Manners
or Live For Success. Today's subject is internal auditing.
up a well-configured firewall is a great idea. It is also good
to track authentication for the VPN and (if you still have it)
dial-up pool. But the firewall and other things work even better
when there are fewer things inside to compromise. Think of it
as layers of defense in reverse - removing potential targets.
It also works better when nobody has circumvented your protections
by some other mechanism. So we'll cover a lot of these things.
Let's start with the firewall. I'm performing a two-step process
for one of my current customers and have done this in the past
for others as well. Intrusion and extrusion testing. My laptop
is sitting inside the firewall, with no special permissions of
any sort -- just a normal workstation from the firewall's point
of view. Using another system, I make an SSH connection to my
Linux box at home and proceed to perform a full 64K TCP Nmap
port scan of my laptop -- with a sniffer running on the laptop.
That's the intrusion test. A simple scan of one system with no
special permissions -- just to see what (if anything) does get
past the firewall. Now, I reverse that. Using a port scanner
on my laptop, I scan my home IP address, knowing that my Snort
system will pick up anything and log it for later analysis. So
right off the bat, I've got a picture of what the effective permissions
"mask" looks like for inbound and outbound access.
We'll assume that this will be dealt with later. If you've got
an organization with multiple geographic sites, you need to check
for rogue Internet connections. There are several ways of doing
this. Here are a few:
up the remote site and ask for whoever is most technical at that
location (the Alpha Geek) and ask him or her how they get to
the Internet. Nothing like the simple approach.
into a remote router or other manageable device to which you
have access and do a traceroute to a public site.
into a remote router or other manageable device, ping your external
firewall, and look at the logs to see where it came from.
up a permit-only ACL (Access Control List) on their router that
permits, in turn: Internal Organization traffic IP range(s),
then wide ranges belonging to popular Internet sites (MSN, Yahoo,
Google, ESPN, Ebay, AOL), then an "everything else"
entry. Wait for anywhere from a few days to weeks and see what
hits you get against the access list. If all of the popular and
"everything else" entries are zero, you've probably
got a rogue Internet connection -- assuming that it's not documented
and official. You did look first, didn't you?
for illicit modems. There are still plenty of them out there.
You'll need what is called a topology report (in the U.S., anyway)
from the phone company(ies) lists all of the incoming phone numbers/lines
that you are paying for. If you talk to whoever handles your
organization's phone bills, they may already have a copy. There
are some very fancy dialing checkers out there, but I still use
ToneLoc (by MuchoMaas and MinorThreat), which is fairly ancient,
but works just fine for me. It's got checks in there for various
PBX signals/tones, but you don't need to look for them in this
effort. It will dial in sequential or pseudo-random order any
block of phone numbers you give it. It's purely a DOS (No, not
Denial Of Service, Disk Operating System) application -- so you'll
have to run it in a command line window. Interesting sidebar
though: I once tried to disassemble the code for ToneLoc, only
to discover that the authors have it wrapped up in its own encryption
scheme. Very clever and discouraging enough to make me not bother.
I'm sure someone reading this will think "lamer" to
him or herself.
for rogue wireless access points. Get a laptop equipped with
NetStumbler, make sure NetStumbler works with whatever wireless
card you have in it against a known wireless access point --
even if you've got to make a trip to Starbucks or similar public
place to test it. Point of clarity here: NetStumbler is not a
wireless security tool; it's more of a wireless survey tool.
There are ways to configure a WAP to evade detection, but if
the owner has done a good job of it, then it's not that great
a threat to your security -- relatively speaking anyway.
for cellular modems? Good idea, but I have no way that I'm aware
of to do that. If someone in the reading audience does know,
please email me here. Just because I don't know how to deal with
such a thing doesn't mean that I don't regard it as a potential
for outbound-oriented remote desktop apps. GoToMyPc and Mionet
(mentioned in a previous blog) make an outbound connection to
a remote site, which effectively allows inbound control to a
system inside. GoToMyPc directs all traffic to "poll.gotomypc.com."
I'm still investigating Mionet, so I don't have all the data
your firewall for inbound remote control connections as well
--mentioned in the same blog as just above.
a port scan internally for the following ports (there are more,
but you've got to start somewhere):
RDP (3389/tcp) (Microsoft Remote Desktop Protocol or Terminal
BackOrifice (31337, 8787, 31338, 54320, 54321, )
SubSeven (1234, 1243, 1999, 2773, 2774, 5873, 6667 (IRC), 6711-6713,
etc.) (You can get free scanners for the bad guy ones)
If you want to look up more, go Treachery.net, which uses the
Neohapsis port listings. If you've got the client side apps,
check to see if any of them let you in with no credentials or
generic domain credentials.
for open file/folder shares. I still use the Legion tool, but
it's not complete, so I've supplemented it with some Perl scripts
and Batch files. The last few years, I've bought (and use) NetScanTools
and NetScanToolsPro -- both from NetscanTools.com, which also
scans for file shares and the like. One Midwestern company I
audited a few years back had over 6 million writeable files discovered
-- mostly from people sharing the root directory. But of those
6 million, between 400-500 of the files had names suggestive
of confidential information. The criteria for these were as follows:
1st pass *.doc, *.xls, *.ppt, *.wpd (Word Perfect), *.vsd (Visio
document). This reduced the list considerably down to the 10s
of thousands instead of millions. The second pass was to check
the file name list for words like "budget," "evaluation,"
"project," "review," "termination,"
"schedule," "offer" and others. This was
what netted us the 400-500 filename list. I recall someone asking
me at the time what those documents contained. My response was
"Are you kidding?" Confidentiality aside, there simply
isn't time to look at that sort of thing, unless you're actually
looking for evidence of criminal wrongdoing -- in which case
that's the wrong approach anyway.
a port 80 (and its variants 81, 82, 83, 85, 88, 8000, 8001, 8080,
etc.) scan to look for rogue Web servers. Many of them will be
printers, print servers and authentication-required devices of
various sorts. If you get prompted for a username and password,
and simple efforts don't get you in, that's good.
-- just to trash the previous paragraph -- there is a Web site
that provided the manufacturer's default account settings for
many, many different types of equipment. Phenoelit.de is the
place to learn how many people in your organization have not
bothered changing the manufacturer's default username/password.
Pretty scary overall.
are lots more things you can do to audit the inside of your network.
But if you go through the list above, and add the other things
that occur to you as you learn what is really going on in your
network, you'll have made a really good start! And if you follow
through, I applaud you.