NetBios explained.doc

(26 KB) Pobierz

The Magic of NetBIOS

In this guide you will learn how to explore the Internet using Windows XP and NetBIOS:

· How to Install NetBIOS <beginnine2a.shtml>

· How to Use Nbtstat <beginnine2b.shtml>

· The Net View Command <beginnine2c.shtml>

· What to Do Once You Are Connected <beginnine2c.shtml>

· How to Break in Using the XP GUI <beginnine2d.shtml>

· More on the Net Commands <beginnine2e.shtml>

· How Crackers Break in as Administrator <beginnine2f.shtml>

· How to Scan for Computers that Use NetBIOS <beginnine2g.shtml>

· How to Play NetBIOS Wargames <beginnine2h.shtml>

· An Evil Genius Tip for Win NT Server Users <beginnine2h.shtml>

· Help for Windows 95, 98, SE and ME Users <beginnine2h.shtml>

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.

How to Break in Using the XP GUI

You could try out the other net commands on Oldguy. Or you can go to the graphical user interface (GUI) of XP. After running the above commands I 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."

NetBios explained.doc

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: