In this guide you will learn how to explore the Internet
using Windows XP and NetBIOS:
* How to Install NetBIOS
* How to Use Nbtstat
* The Net View Command
* What to Do Once you Are Connected
* More on the Net Commands
* How Crackers Log on as Administrator
* How to Scan for Computers that Use NetBIOS
* How to Play NetBIOS Hacker Wargames
* An Evil Genius Tip for Win NT Server Users
* Help for Windows 95, 98, SE and ME Users
Not many computers are reachable over the Internet using NetBIOS commands -
maybe only a few million. But what the heck, a few million is enough to keep a
hacker from getting bored. And if you know what to look for, you will discover
that there are a lot of very busy hackers and Internet worms searching for
computers they can break into by using NetBIOS commands. By learning the dangers
of NetBIOS, you can get an appreciation for why it is a really, truly BAD!!!
idea to use it.
***************** Newbie note: a worm is a program that reproduces itself. For example,
Code Red automatically searched over the Internet for vulnerable Windows
computers and broke into them. So if you see an attempt to break into your
computer, it may be either a human or a worm.
*****************
If you run an intrusion detection system (IDS) on your computer, you are certain
to get a lot of alerts of NetBIOS attacks. Here's an example:
The firewall has blocked Internet access to your computer (NetBIOS Session) from
10.0.0.2 (TCP Port 1032) [TCP Flags: S].
Occurred: 2 times between 10/29/2002 7:38:20 AM and 10/29/2002 7:46:18 AM
A Windows NT server on my home network, which has addresses that all start with
10.0.0, caused these alerts. In this case the server was just doing its innocent
thing, looking for other Windows computers on my LAN (local area network) that
might need to network with it. Every now and then, however, an attacker might
pretend to have an address from your internal network even though it is
attacking from outside.
If a computer from out on the Internet tries to open a NetBIOS session with one
of mine, I'll be mighty suspicious. Here's one example of what an outside attack
may look like:
The firewall has blocked Internet access to your computer (NetBIOS Name) from
999.209.116.123 (UDP Port 1028).
Time: 10/30/2002 11:10:02 AM (The attacker's IP address has been altered to
protect the innocent or the guilty, as the case may be.)
Want to see how intensely crackers and worms are scanning the Internet for
potential NetBIOS targets? A really great and free IDS for Windows that is also
a firewall is Zone Alarm. You can download it for free from
http://www.zonelabs.com . You can set it
to pop up a warning on your screen whenever someone or some worm attacks your
computer. You will almost certainly get a NetBIOS attack the first day you use
your IDS.
Do you need to worry when a NetBIOS attack hits? Only if you have enabled
NetBIOS and Shares on your computer. Unfortunately, in order to explore other
computers using NetBIOS, you increase the danger to your own computer from
attack by NetBIOS. But, hey, to paraphrase a famous carpenter from Galilee, he
who lives by the NetBIOS gets hacked by the NetBIOS.
******************** Newbie note: NetBEUI (NetBIOS Extended User Interface) is an out-of-date,
crummy, not terribly secure way for Windows computers to communicate with each
other in a peer-to-peer mode. NetBIOS stands for network basic input/output
system.
Newbie note: Shares are when you make it so other computers can access
files and directories on your computer. If you set up your computer to use
NetBIOS, in Win XP using the NTFS (new technology file system)you can share
files and directories by bringing up My Computer. Click on a directory - which
in XP is called a "folder". In the left-hand column a task will appear called
"Share this folder". By clicking this you can set who can access this folder,
how many people at a time can access it, and what they can do with the folder.
********************
There are a number of network exploration commands that only NetBIOS uses. We
will show how to use nbtstat and several versions of the net command.
How to Install NetBIOS
You might have to make changes on your system in order to use these commands.
Here's how to enable NetBIOS for Windows XP. (If you are stuck with Windows 95,
98, SE or ME, see the end of this Guide for how to enable NetBIOS.) Click:
Control Panel -> Network Connections
There are two types of network connections that may appear here: "Dial-up" and
"LAN or High-Speed Internet".
************** Newbie note: A dial-up connection uses a modem to reach the Internet. LAN
stands for local area network. It's what you have if two or more computers are
linked to each other with a cable instead of modems. Most schools and businesses
have LANs, as well as homes with Internet connection sharing. A DSL or cable
modem connection will also typically show up as a LAN connection.
**************
To configure your connections for hacking, double click on the connection you
plan to use. That brings up a box that has a button labeled "Properties".
Clicking it brings up a box that says "This connection uses the following
items:"
You need to have both TCP/IP and NWLink NetBIOS showing. If NWLink NetBIOS is
missing, here's how to add it. Click Install -> Protocol -> Add NWlink/IPX/SPX/NetBIOS
Compatible Transport Protocol.
************** Newbie note: NWLink refers to Novell's Netware protocol for running a
LAN.
**************
How to Use Nbtstat
To get started, bring up the cmd.exe command. Click Start -> Run and type
cmd.exe in the command line box. This brings up a black screen with white
letters. Once it is up, we will play with the nbtstat command. To get help for
this command, just type:
C:\>nbtstat help
One way to use the nbtstat command is to try to get information from another
computer using either its domain name (for example test.target.com), its
numerical Internet address (for example, happyhacker.org's numerical address is
206.61.52.30), or its NetBIOS name (if you are on the same LAN).
C:\>nbtstat -a 10.0.0.2
Local Area Connection:
Node IpAddress: [10.0.0.1] Scope Id: []
NetBIOS Remote Machine Name Table
Name Type Status
---------------------------------------------
OLDGUY <00> UNIQUE Registered
OLDGUY <20> UNIQUE Registered
WARGAME <00> GROUP Registered
INet~Services <1C> GROUP Registered
IS~OLDGUY......<00> UNIQUE Registered
OLDGUY <03> UNIQUE Registered
WARGAME <1E> GROUP Registered
ADMINISTRATOR <03> UNIQUE Registered
MAC Address = 52-54-00-E4-6F-40
What do these things tell us about this computer? Following is a table
explaining the codes you may see with an nbtstat command (taken from the MH Desk
Reference, written by the Rhino9 team).
Name Number Type Usage
=========================================================
<computername> 00 U Workstation Service
<computername> 01 U Messenger Service
<\\_MSBROWSE_> 01 G Master Browser
<compname> 03 U Messenger Service
<computername> 06 U RAS Server Service
<computername> 1F U NetDDE Service
<computername> 20 U File Server Service
<computername> 21 U RAS Client Service
<computername> 22 U Exchange Interchange
<computername> 23 U Exchange Store
<computername> 24 U Exchange Directory
<computername> 30 U Modem Sharing Server Service
<computername> 31 U Modem Sharing Client Service
<computername> 43 U SMS Client Remote Control
<computername> 44 U SMS Admin Remote Control Tool
<computername> 45 U SMS Client Remote Chat
<computername> 46 U SMS Client Remote Transfer
<computername> 4C U DEC Pathworks TCPIP Service
<computername> 52 U DEC Pathworks TCPIP Service
<computername> 87 U Exchange MTA
<computername> 6A U Exchange IMC
<computername> BE U Network Monitor Agent
<computername> BF U Network Monitor Apps
<username> 03 U Messenger Service
<domain> 00 G Domain Name
<domain> 1B U Domain Master Browser
<domain> 1C G Domain Controllers
<domain> 1D U Master Browser
<domain> 1E G Browser Service Elections
<INet~Services> 1C G Internet Information Server
<IS~Computer_name>00 U Internet Information Server
To keep this Guide from being ridiculously long, we'll just explain a few of the
things what we learned when we ran nbtstat -a against 10.0.0.2:
* it uses NetBIOS
* its NetBIOS name is Oldguy
* one of the users is named Administrator
* it runs a web site with Internet Information Server, and maybe an ftp - file
transfer protocol -- server
* it is a member of the domain Wargame
* it is connected on a local area network and we accessed it through an
Ethernet network interface card (NIC) with a MAC Address of 52-54-00-E4-6F-40.
When using nbtstat over the Internet, in most cases it will not find the correct
MAC address. However, sometimes you get lucky. That is part of the thrill of
legal hacker exploration. OK, OK, maybe getting a thrill out of a MAC address
means I'm some kind of a freak. But if you are reading this, you probably are
freaky enough to be a hacker, too.
************** Newbie note: MAC stands for media access control. In theory every NIC
ever made has a unique MAC address, one that no other NIC has. In practice,
however, some manufacturers make NICs that allow you to change the MAC address.
**************
************** Evil Genius tip: sneak your computer onto a LAN and use it to find the
MAC address of a very interesting computer. Crash it, then give yours the same
MAC, NetBIOS name and Internet address as the very interesting computer. Then
see what you can do while faking being that computer. That's why I get a charge
out of discovering a MAC address, so stop laughing at me already.
**************
**************
You can get fired, expelled, busted and catch cooties warning: Faking all that
stuff is something you would be better off doing only on your own test network,
or with written permission from the owner of the very interesting computer.
**************
Now that we know some basic things about computer 10.0.0.2, also known as Oldguy,
we can do some simple things to learn more. We can connect to it with a web
browser to see what's on the web site, and with ftp to see if it allows
anonymous users to download or upload files. In the case of Oldguy, anyone can
browse the web site. However, when we try to connect to its ftp server with
Netscape by giving the location ftp://10.0.0.2, it
returns the message "User Mozilla@ cannot log in.
************** Newbie note: The people who programmed Netscape have always called it
Mozilla, after a famous old movie monster. As a joke they have stuck obscure
mentions of Mozilla into the operations of Netscape. Mozilla lovers recently
spun off a pure Mozilla browser project that has the web site
http://www.mozilla.org.
**************
The Net View Command
Now let's have some serious fun. Netscape (or any browser or ftp program) uses
TCP/IP to connect. What happens if we use NetBIOS instead to try to download
files from Oldguy's ftp server?
Let's try some more NetBIOS commands:
C:\>net view \\10.0.0.2
System error 53 has occurred.
The network path was not found.
I got this message because my firewall blocked access to Oldguy, giving the
message:
The firewall has blocked Internet access to 10.0.0.2 (TCP Port 445) from your
computer [TCP Flags: S].
There's a good reason for this. My firewall/IDS is trying to keep me from
carelessly making my computer a part of some stranger's LAN. Keep in mind that
NetBIOS is a two-way street. However, I want to run this command, so I shut down
Zone Alarm and give the command again:
C:\>net view \\10.0.0.2
Shared resources at \\10.0.0.2
Share name Type Used as Comment
--------------------------------------------------------
ftproot Disk
InetPub Disk
wwwroot Disk
The command completed successfully.
This is a list of shared directories. Oooh, look at that, the ftp server is
shared. Does this mean I can get in? When setting shares on a Windows NT server,
the default choice is to allow access to read, write and delete files to
everyone. So sometimes a sysadmin carelessly fails to restrict access to a
share.
What is really important is that we didn't need a user name or password to get
this potentially compromising information.
Let's establish an anonymous connection to Oldguy, meaning we connect without
giving it a user name or password:
C:\>net use \\10.0.0.2\ipc$
Local name
Remote name \\10.0.0.2\IPC$
Resource type IPC
Status OK
# Opens 0
# Connections 1
The command completed successfully.
We are connected!
**********************
Newbie note: IPC (ipc$) stands for "Inter Process Connector", used to set up
connections across a network between Windows computers using NetBIOS.
**********************
What to Do Once You Are Connected
So far we haven't quite been breaking the law, although we have been getting
pretty rude if the owner of that target computer hasn't given us permission to
explore. What if we want to stop pushing our luck and decide to disconnect? Just
give the message:
C:\>net session \\10.0.0.2 /delete
Of course you would substitute the name or number of the computer to which you
are connected for 10.0.0.2.
What if you want to stay connected? Oldguy will let you stay connected even if
you do nothing more. By contrast, a login to a Unix/Linux type computer will
normally time out and disconnect you if you go too long without doing anything.
You could try out the other net commands on Oldguy. Or you can go to the
graphical user interface (GUI) of XP. Click My Computer, then My Network Places
and there you'll find the victim, er, I mean, target computer. By clicking on
it, I discover that ftproot has been shared to - everyone!
Let's say you were to get this far investigating some random computer you found
on the Internet. Let's say you had already determined that the ftp server isn't
open to the public. At this moment you would have a little angel sitting one
shoulder whispering "You can be a hero. Email the owner of that computer to tell
him or her about that misconfigured ftproot."
On the other shoulder a little devil is sneering, "Show the luser no mercy.
Information should be free. Because I said so, that's why. Hot darn, are those
spreadsheets from the accounting department? You could make a lot of bucks
selling those files to a competitor, muhahaha! Besides, you're so ugly that
future cellmate Spike won't make you be his girlfriend."
Some hackers might think that because ftproot is shared to the world that it is
OK to download stuff from it. However, if someone were to log in properly to
that ftp server, he or she would get the message "Welcome to Oldguy on Carolyn
Meinel's LAN. Use is restricted to only those for whom Meinel has assigned a
user name and password." This warning logon banner is all a computer owner needs
to legally establish that no one is allowed to just break in. It won't impress a
judge if a cracker says "The owner was so lame that her computer deserved to get
broken into" or "I'm so lame that I forgot to try to use the ftp server the
normal way."
More on the Net Commands
Let's get back to the net command. There are many forms of this command. In XP
you can learn about them with the command:
C:\>net help
The syntax of this command is:
NET HELP
command
-or-
NET command /HELP
Commands available are:
NET ACCOUNTS NET HELP NET SHARE
NET COMPUTER NET HELPMSG NET START
NET CONFIG NET LOCALGROUP
NET STATISTICS
NET CONFIG SERVER NET NAME NET STOP
NET CONFIG WORKSTATION NET PAUSE NET TIME
NET CONTINUE NET PRINT NET USE
NET FILE NET SEND NET USER
NET GROUP NET SESSION NET VIEW
NET HELP SERVICES lists some of the services you can start.
NET HELP SYNTAX explains how to read NET HELP syntax lines.
NET HELP command | MORE displays Help one screen at a time.
How Crackers Log on as Administrator
As we look around Oldguy further, we see that there's not much else an anonymous
user can do to it. We know that there is a user named Administrator. What can we
do if we can convince Oldguy that we are Administrator?
****************** Newbie note: in Windows NT, 2000 and XP, the Administrator user has total
power over its computer, just as root has total power over a Unix/Linux type
computer. However, it is possible to change the name of Administrator so an
attacker has to guess which user has all the power.
******************
Let's try to log in as Administrator by guessing the password. Give the command:
C:\>net use \\10.0.0.2\ipc$ * /user:Administrator
Type the password for \\10.0.0.2\ipc$:
System error 1219 has occurred.
Multiple connections to a server or shared resource by the same user, using more
than one user name, are not allowed. Disconnect all previous connections to the
server or shared resource and try again.
This means that someone else is currently logged onto this server who has
Administrator rights. Furthermore, this person is probably watching me on an IDS
and thinking up terrible things to do to me. Eeep! Actually this is all going on
inside my hacker lab - but you get the idea of what it could be like when trying
to invade a computer without permission.
I discover that whether I guess the password correctly or not, I always get the
same error message. This is a good safety feature. On the other hand, one of the
users is named Administrator. This is a bad thing for the defender. When you
first set up a Windows NT or 2000 server, there is always a user called
Administrator, and he or she has total power over that computer. If you know the
all-powerful user is named Administrator, you can try guessing the password
whenever no one is logged on with Administrator powers.
Computer criminals don't waste time guessing by hand. They use a program such as
NAT or Legion to get passwords. These programs are why smart NT administrators
rename their Administrator accounts and choose hard passwords. Also, this kind
of persistent attack will be detected by an intrusion detection system, making
it easy to catch criminals at work.
********************
You can get expelled warning: What if you are a student and you want to save
your school from malicious code kiddies who steal tests and change grades? It is
important to get permission *in writing* before you test the school's network.
Even then, you still must be careful to be a model student. If you act up, cut
classes - you know what I mean - the first time a cracker messes up the network,
who do you think they will suspect? Yes, it's unfair, and yes, that is the way
the world works.
********************
How to Scan for Computers that Use NetBIOS
How do you find Windows computers that are running NetBIOS? Your tool of choice
is a port scanner. Any computer that is running something on port 139 is likely
(but not certain) to be using NetBIOS. Most crackers use nmap to port scan. This
tool runs on Unix/Linux type computers. You can get it at
http://www.insecurity.org . There is
also a Windows version of nmap, but it isn't very good. A better choice for
Windows is Whats Up from
http://www.ipswitch.com . You can get a one month free trial of it.
Here's an example of an nmap scan of Oldguy:
test-box:/home/cmeinel # nmap -sTU 10.0.0.2
Starting nmap V. 3.00 ( www.insecure.org/nmap/ )
Interesting ports on (10.0.0.2):
(The 3060 ports scanned but not shown below are in state: closed)
Port State Service
21/tcp open ftp
70/tcp open gopher
80/tcp open http
135/tcp open loc-srv
135/udp open loc-srv
137/udp open netbios-ns
138/udp open netbios-dgm
139/tcp open netbios-ssn
500/udp open isakmp
Nmap run completed -- 1 IP address (1 host up) scanned in 8 seconds
As you can see from this scan, three ports are identified with NetBIOS. This
tells us that we could set nmap to scan a large number of Internet addresses,
only looking for port 139 on each. To learn how to set up nmap to run this way,
in your Unix or Linux shell give the command "man nmap".
********************
You can get punched in the nose warning: If you use a port scanner against
networks that haven't given you permission to scan, you will be waving a red
flag that says "Whaddaya wanna bet I'm a computer criminal?" You can't get
arrested for merely port scanning, but people who don't like being scanned might
get you kicked off your Internet service provider.
You can get really, big time, punched in the nose warning: If you visit the same
computer or LAN really often to see what's new and to try different things, even
if you don't break the law you'd better be doing it with the permission of the
owner. Otherwise you may make enemies who might crash or destroy your operating
system. And that is only what they may do when feeling mellow. After a night of
hard drinking - well, you don't want to find out.
********************
How to Play NetBIOS Wargames
What if you want to challenge your friends to a hacker wargame using NetBIOS?
The first thing to do is *don't* email me asking me to break in for you. Sheesh.
Seriously, I get emails from people claiming to have permission from their
girlfriend/boyfriend and begging me to help them break in. You can read their
hilarious pleas for help at
http://happyhacker.org/sucks/ .
The way to run a hacker wargame over the Internet is first, get permission from
your Internet provider so they don't kick you off for hacking. They probably run
an IDS that scans users for suspicious activity. They probably hate malicious
hackers. Enough said.
Second, you and your friends are likely to be at a different Internet address
every time you log on. Your safest way to play over the Internet is for each
player to get an Internet address that is the same every time he or she logs on:
a "static" address. This way you won't accidentally break into someone else's
computer.
You have to arrange with your Internet provider to get a static address.
Normally only a local provider can do this for you. A big advantage of using a
local provider is you can make friends with the people who work there - and they
are probably hackers.
If you live in an apartment building or dormitory with other hackers, you can
play break-in games without using the Internet. Set up a LAN where you can play
together. For example, you can string Ethernet cable from window to window. To
learn how to set up a Windows Ethernet LAN, see
http://happyhacker.org/gtmhh/winlan.shtml .
Or you could set up a wireless LAN. With wireless you never know who might come
cruising with a laptop down the street by your home or business and break in.
That can make a wargame lots more fun. For help on how to break into wireless
LANs (it's pathetically easy and with care can be borderline legal), see
http://www.wardriving.com .
************** Evil genius tip: Attack using a Win NT server with the Microsoft Resource
Kit installed. Heh, heh. With it you can give the command:
C:\>Local Administrators \\<targetbox.com>
This should show all user accounts with administrator rights on targetbox.com.
C:\>Global Administrators \\<targetbox.com >
This should show all user accounts with Domain administrative rights.
These are exceptionally worth compromising, because with one Domain
administrative password you will be able to control many resources among NT
servers, workstations, and Win 95/98 computers.
I've tried to install the Resource Kit on XP Professional, but it wasn't
compatible.
Another option is to install hacker tools such as Red Button and DumpACL, which
extract information on user names, hashes, and which services are running on a
given machine.
**************
Help for users of Windows 95, 98, SE or ME
To enable NetBIOS, click
Control Panel -> Network -> Protocols
If you see both NetBEUI and TCP/IP, you are already using NetBIOS. If not, add
NetBEUI.
To bring up the command screen, click Start -> Run and type in command.com.
____________________________________________________________
Where are those back issues of GTMHHs and Happy Hacker Digests? Check out the
official Happy Hacker Web page at
http://www.happyhacker.org. We are against computer crime. We support good,
old-fashioned hacking of the kind that led to the creation of the Internet and a
new era of freedom of information. But we hate computer crime. So don't email us
about any crimes you may have committed!
Copyright 2002 Carolyn Meinel. You may forward, print out or post this GUIDE TO
(mostly) HARMLESS HACKING on your Web site as long as you leave this notice at
the end.
