Ethical Hacking
Module V
System Hacking
Module Objective
Understand the following
Remote password guessing
Eavesdropping
Denial of Service
Buffer overflows
Privilege escalation
Password cracking
keystroke loggers
sniffers
Remote control and backdoors
Port re direction
Covering tracks
Hiding files
Administrator Password Guessing
Assuming that NetBIOS TCP139 port is open, the most effective method of breaking into NT/2000 is password guessing.
Attempting to connect to an enumerated share (IPC$, or C$) and trying username/password.
Default Admin$, C$, %Systemdrive% shares are good starting point.
Performing automated password guessing
Performing automated password guessing is easy-simple loop using the NT/2000 shell for command based on the standard NET USE syntax.
1. Create a simple username and password file.
2. Pipe this file into FOR command
C:> FOR /F "token=1, 2*" %i in (credentials.txt)
do net use \targetIPC$ %i /u: %j
Tool: Legion
Legion automates the password guessing in NetBIOS sessions. Legion will scan multiple Class C IP address ranges for Windows shares and also offers a manual dictionary attack tool.
Hacking tool: NTInfoScan (now CIS)
NTInfoScan is a security scanner for NT 4.0 is a vulnerability scanner that produces an HTML based report of security issues found on the target system and further information.
Password guessing Countermeasures
Block access to TCP and UDP ports 135-139.
Disable bindings to Wins client on any adapter.
Use complex passwords
Log failed logon attempts in Event viewer - Security log full event 529 or 539 - Logon/Logoff
Monitoring Event Viewer Logs
Logging is of no use if no one ever analyzes the logs
VisualLast from www.foundstone.com formats the event logs visually
Password Sniffing
Password guessing is hard work. Why not just sniff credentials off the wire as users log in to a server and then replay them to gain access?
Hacking Tool: LOphtcrack
LC4 is a password auditing and recovery package distributed by @stake software. SMB packet capture listens to the local network segment and captures individual login sessions.
With LOphtcrack password cracking engine anyone can sniff the ire for extended periods is most guaranteed to obtain Administrator status in matter of days.
Hacking Tool: KerbCrack
KerbCrack consists of two programs, kerbsniff and kerbcrack. The sniffer listens on the network and captures Windows 2000/XP Kerberos logins. The cracker can be used to find the passwords from the capture file using a bruteforce attack or a dictionary attack.
Privilege Escalation
If an attacker gains access to the network using non-admin user account, the next step is to gain higher privilege to that of an administrator.
This is called privilege escalation
Tool: GetAdmin
GetAdmin.exe is a small program that adds a user to the local administrators group.
It uses low-level NT kernel routine to set a globalflag allowing access to any running process.
You need to logon to the server console to execute the program.
The GetAdmin.exe is run from the command line or from a browser.
This only works with Nt 4.0 Service pack 3.
Tool: hk.exe
The hk.exe utility exposes a Local Procedure Call flaw in NT.
A non-admin user can be escalated to administrators group using hk.exe
Manual Password Cracking Algorithm
Find a valid user
Create a list of possible passwords
Rank the passwords from high probability to low
Key in each password
If the system allows you in - Success
Else try till success
Automatic Password Cracking Algorithm
Find a valid user
Find encryption algorithm used
Obtain encrypted passwords
Create list of possible passwords
Encrypt each word
See if there is a match for each user ID
Repeat steps 1 through 6
Password Types
Passwords that contain only letters.
Passwords that contain only numbers.
Passwords that contain only special characters.
Passwords that contain letters and numbers.
Passwords that contain only letters and special characters.
Passwords that contain only special characters and numbers.
Passwords that contain letters, special characters and numbers.
Types of Password Attacks
Dictionary attack
Brute force attack
Hybrid attack
Social engineering
Shoulder surfing
Dumpster diving
Cracking NT/2000 passwords
SAM file in Windows NT/2000 contains the usernames and encrypted passwords. The SAM file is located at %systemroot%system32config directory
The file is locked when the OS is running.
Booting to an alternate OS
NTFSDOS (www.sysInternals.com) will mount any NTFS partition as a logical drive.
Backup SAM from the Repair directory
Whenever rdisk /s is run, a compressed copy of the SAM called SAM._ is created in %systemroot% epair. Expand this file using c:>expand sam._sam
Extract the hashes from the SAM
Use LOphtcrack to hash the passwords.
Redirecting SMB Logon to the Attacker
Eavesdropping on LM responses becomes much easier if the attacker can trick the victim to attempt Windows authentication of the attacker`s choice.
Basic trick is to send an email message to the victim with an embedded hyperlink to a fraudulent SMB server.
When the hyperlink is clicked, the user unwittingly sends his credentials over the network.
Hacking Tool: SMBRelay
SMBRelay is essentially a SMB server that can capture usernames and password hashes from incoming SMB traffic.
It can also perform man-in-the-middle (MITM) attacks.
You must disable NetBIOS over TCP/IP and block ports 139 and 445.
Start the SMBRelay server and listen for SMB packets:
c:>smbrelay /e
c:>smbrelay /IL 2 /IR 2
An attacker can access the client machine by simply connecting to it via relay address using: c:> net use * \c$
SMBRelay man-in-the-middle Scenario
The attacker in this setting sets up a fraudulent server at 192.168.234.251, a relay address of 192.168.234.252 using /R, and a target server address of 192.168.234.34 with /T.
c:> smbrelay /IL 2 /IR /R 192.168.234.252 /T 192.168.234.34
When a victim client connects to the fraudulent server thinking it is talking to the target, MITM server intercepts the call, hashes the password and passes the connection to the target server.
SMBRelay Weakness & Countermeasures
The problem is to convince a victim`s client to authenticate to the MITM server
You can send a malicious e-mail message to the victim client with an embedded hyperlink to the SMBRelay server`s IP address.
Another solution is ARP poisoning attack against the entire segment causing all of the systems on the segment to authenticate through the fraudulent MITM server
Countermeasures
Configure Windows 2000 to use SMB signing.
Client and server communication will cause it to cryptographically sign each block of SMB communications.
These settings are found under Security Policies /Security Options
Hacking Tool: SMB Grind
SMBGrind increases the speed of LOphtcrack sessions on sniffer dumps by removing duplication and providing a facility to target specific users without having to edit the dump files manually.
Hacking Tool: SMBDie
SMBDie tool crashes computers running Windows 2000/XP/NT by sending specially crafted SMB request.
Hacking Tool: NBTDeputy
NBTDeputy register a NetBIOS computer name on the networkand is ready to respond to NetBT name-query requests.
NBTdeputy helps to resolve IP address from NetBIOS computer name. It`s similar to Proxy ARP.
This tool works well with SMBRelay.
For example, SMBRelay runs on a computer as ANONYMOUS-ONE and the IP address is 192.168.1.10 and NBTDeputy is also ran and 192.168.1.10 is specified. SMBRelay may connect to any XP or .NET server when the logon users access "My Network Places"
NeBIOS DoS Attack
Sending a `NetBIOS Name Release` message to the NetBIOS Name Service (NBNS, UDP 137) on a target NT/2000 machine forces it to place its name in conflict so that the system will no longer will be able to use it.
This will block the client from participating in the NetBIOS network.
Tool: nbname
NBName can disable entire LANs and prevent machines from rejoining them.
Nodes on a NetBIOS network infected by the tool will think that their names already are being used by other machines.

Hacking Tool: John the Ripper
It is a command line tool designed to crack both Unix and NT passwords. John is extremely fast and free
The resulting passwords are case insensitive and may not represent the real mixed-case password.
What is LanManager Hash?
Example: Lets say your password is: `123456qwerty`
When this password is encrypted with LM algorithm, it is first converted to all uppercase: `123456QWERTY`
The password is padded with null (blank) characters to make it 14 character length: `123456QWERTY_`
Before encrypting this password, 14 character string is split into half: `123456Q and WERTY_`
Each string is individually encrypted and the results concatenated.
`123456Q` = 6BF11E04AFAB197F
`WERTY_` = F1E9FFDCC75575B15
The hash is 6BF11E04AFAB197FF1E9FFDCC75575B15
Note: The first half of the hash contains alpha-numeric characters and it will take 24 hrs to crack by LOphtcrack and second half only takes 60 seconds.
Password Cracking Countermeasures
Enforce 7-12 character alpha-numeric passwords.
Set the password change policy to 30 days.
Physically isolate and protect the server.
Use SYSKEY utility to store hashes on disk.
Monitor the server logs for brute force attacks on user accounts.
Keystroke Loggers
If all other attempts to sniff out domain privileges fail, then keystroke logger is the solution.
Keystroke loggers are stealth software that sits between keyboard hardware and the operating system, so that they can record every key stroke.
There are two types of keystroke loggers:
1. Software based and
2. Hardware based.
Spy ware: Spector (www.spector.com)
Spector is a spy ware and it will record everything anyone does on the internet.
Spector automatically takes hundreds of snapshots every hour, very much like a surveillance camera. With spector, you will be able to see exactly what your surveillance targets have been doing online and offline.
Spector works by taking a snapshot of whatever is on your computer screen and saves it away in a hidden location on your computer`s hard drive.
Hacking Tool: eBlaster (www.spector.com)
eBlaster lets you know EXACTLY what your surveillance targets are doing on the internet even if you are thousands of miles away.
eBlaster records their emails, chats, instant messages, websites visited and keystrokes typed and then automatically sends this recorded information to your own email address.
Within seconds of them sending or receiving an email, you will receive your own copy of that email.
IKS Software Keylogger
Hacking Tool: Hardware Key Logger (www.keyghost.com)
The Hardware Key Logger is a tiny hardware device that can be attached in between a keyboard and a computer.
It keeps a record of all key strokes typed on the keyboard. The recording process is totally transparent to the end user.
Anti Spector (www.antispector.de)
This tool will detect Spector and detect them from your system.
Hacking Tool: RootKit
What if the very code of the operating system came under the control of the attacker?
The NT/2000 rootkit is built as a kernel mode driver which can be dynamically loaded at run time.
The NT/2000 rootkit runs with system privileges, right at the core of the NT kernel, so it has access to all the resources of the operating system.
The rootkit can also:
hide processes (that is, keep them from being listed)
hide files
hide registry entries
intercept keystrokes typed at the system console
issue a debug interrupt, causing a blue screen of death
redirect EXE files
Planting the NT/2000 Rootkit
The rootkit contains a kernel mode device driver, called _root_.sys and a launcher program, called deploy.exe
After gaining access to the target system, he will copy _root_.sys and deploy.exe onto the target system and execute deploy.exe
This will install the rootkit device driver and start it up. The attacker later deletes deploy.exe from the target machine.
The attacker can then stop and restart the rootkit at will by using the commands net stop _root and net start _root_
Once the rootkit is started, the file _root_.sys stops appearing in the directory listings. The rootkit intercepts the system calls for listing files and hides all files beginning with _root_ from display.

Rootkit Countermeasures
Back up critical data (not binaries!) Wipe everything clean and reinstall OS/applications from trusted source.
Don’t rely on backups, because you could be restoring from trojaned software.
Keep a well documented automated installation procedure.
Keep availability of trusted restoration media.
Covering Tracks
Once intruders have successfully gained Administrator access on a system, they will try to cover the detection of their presence.
When all the information of interest has been stripped from the target, they will install several back doors so that easy access can be obtained in the future.
Disabling Auditing
First thing intruders will do after gaining Administrator privileges is to disable auditing.
NT Resource Kit`s auditpol.exe tool can disable auditing using command line.
At the end of their stay, the intruders will just turn on auditing again using auditpol.exe
Clearing the Event log
Intruders can easily wipe out the logs in the event viewer
Event viewer on the attackers host can open, read and clear logs of the remote host.
This process will clear logs of all records but will leave one record stating that the event log has been cleared by `Attacker`
Tool: elsave.exe
elsave.exe utility is a simple tool for clearing the event log. The following syntax will clear the security log on the remote server `rovil` ( correct privileges are required on the remote system)
Save the system log on the local machine to d:system.log and then clear the log:
elsave -l system -F d:system.log –C
Save the application log on \serv1 to \serv1d$application.log:
elsave -s \serv1 -F d:application.log
Hacking Tool: WinZapper
Wizapper is a tool that an attacker can use to erase event records selectively from the security log in Windows 2000.
To use the program, the attacker runs winzapper.exe and marks the event records to be deleted, then he presses `delete events` and `exit`. Presto the events disappear.
To sum things up: after an attacker has gained Administrators access to the system, one simply cannot trust the security log!
Evidence Eliminator
Evidence Eliminator is an easy to use powerful and flexible data cleansing system for Windows PC.
Daily use protects you from unwanted data becoming permanently hidden in your PC.
It cleans recycle bins, Internet cache, system files, temp folders etc.
Hiding Files
There are two ways of hiding files in NT/2000.
1. Attrib
use attrib +h [file/directory]
2. NTFS Alternate Data Streaming
NTFS files system used by Windows NT, 2000 and XP has a feature Alternate Data Streams - allow data to be stored in hidden files that are linked to a normal visible file.
Streams are not limited in size and there can be more than one stream linked to a normal file.
Creating Alternate Data Streams
Start by going to the command line and typing notepad test.txt
Put some data in the file, save the file, and close Notepad.
From the command line, type dir test.txt and note the file size.
Next, go to the command line and type notepad test.txt:hidden.txt Type some text into Notepad, save the file, and close.
Check the file size again and notice that it hasn’t changed!
If you open test.txt, you see your original data and nothing else.
If you use the type command on the filename from the command line, you still get the original data.
If you go to the command line and type type test.txt:hidden.txt you get an error.
Tools: ADS creation and detection
makestrm.exe moves the physical contents of a file to its stream.

ads_cat from Packet Storm is a utility for writing to NTFS`s Alternate File Streams and includes ads_extract, ads_cp, and ads_rm, utilities to read, copy, and remove data from NTFS alternate file streams.
Mark Russinovich at www.sysinternals.com has released freeware utility Streams which displays NTFS files that have alternate streams content.
Heysoft has released LADS (List Alternate Data Streams), which scans the entire drive or a given directory. It lists the names and size of all alternate data streams it finds.
NTFS Streams countermeasures
Deleting a stream file involves copying the `front` file to a FAT partition, then copying back to NTFS.
Streams are lost when the file is moved to FAT Partition.
LNS.exe from (http://nt security.nu/cgi-bin/download/lns.exe.pl) can detect streams.
Stealing Files using Word Documents
Anyone who saves a word document has a potentially new security risk to consider – one that no current anti-virus or Trojan scanner will turn up.
The contents of the files on victim`s hard drives can be copied and sent outside your firewall without even their knowing.
The threat takes advantage of a special feature of word called field codes.
Here`s how it might work: Someone sends victim a Word document with a field-code bug. The victim opens the file in Word, saves it (even with no changes) , then sends it back to the originator.
Field Code Counter measures
Use Hidden Field Detector. It`s available free at:
http://www.woodyswatch.com/util/sniff/
Hidden field Detector upon installation will install itself on your Word Tools Menu.
It scans your documents for potentially troublesome field codes, which you cant see easily and even warns you when it finds something suspicious.
What is Steganography?
The process of hiding data in images is called Steganography.
The most popular method for hiding data in files is to utilize graphic images as hiding place.
Attackers can embed information such as:
1.Source code for hacking tool
2.List of compromised servers
3.Plans for future attacks
4..your grandma/s secret cookie recipe
Tool : Image Hide
ImageHide is a steganography program. Can Hide loads of text in images.
Simple encrypt and decrypt of data
Even after adding bytes of data, there is no increase in image size.
Image looks the same to normal paint packages
Loads and saves to files and gets past all the mail sniffers.
Tool: Mp3Stego
MP3Stego will hide information in MP3 files during the compression process.
The data is first compressed, encrypted and then hidden in the MP3 bit stream.
Tool: Snow.exe
Snow is a whitespace steganography program and is used to conceal messages in ASCII text by appending whitespace to the end of lines.
Because spaces and tabs are generally not visible in text viewers, the message is effectively hidden from casual observers. If the built in encryption is used, the message cannot be read even if it is detected.
Tool: Camera/Shy
Camera/Shy works with Windows and Internet Explorer and lets users share censored or sensitive information buried within an ordinary gif image.
The program lets users encrypt text with a click of the mouse and bury the text in an image. The files can be password protected for further security.
Viewers who open the pages with the Camera/Shy browser tool can then decrypt the embedded text on the fly by double-clicking on the image and supplying a password.
Steganography Detection
Stegdetect is an automated tool for detecting steganographic content in images.
It is capable of detecting different steganographic methods to embed hidden information in JPEG images.
Stegbreak is used to launch dictionary attacks against Jsteg-Shell, JPHide and OutGuess 0.13b.
Tool: dskprobe.exe
Windows 2000 Installation CD-ROM
dskprobe.exe is a low level disk editor located in Support Tools directory.
Steps to read the efs temp contents:
1.Launch dskprobe and open the physical drive to read.
2.Click the Set Active button adjustment to the drive after it populates the handle `0`.
3.Click Tools -> Search sectors and search for string efs0.tmp (in sector 0 at the end of the disk).
4.You should select Exhaustive Search, Ignore Case and Unicode characters.
Buffer overflows
A buffer overrun is when a program allocates a block of memory of a certain length and then tries to stuff too much data into the buffer, with extra overflowing and overwriting possibly critical information crucial to the normal execution of the program. Consider the following source code:
When the source is compiled and turned into a program and the program is run, it will assign a block of memory 32 bytes long to hold the name string.
Buffer overflow will occur if you enter:
`AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
Outlook Buffer Overflow
There is a vulnerability in Microsoft Outlook client. The attacker sends an e-mail with a malformed header that causes buffer overflow to occur.
1. It will cause the victim`s machine to crash or
2.Cause arbitrary code to run on the victim`s computer.
Affects the following versions:
Microsoft Outlook versions 97/98 and 2000.
Microsoft Outlook Express 4.0, 4.01. 5.0 and 5.01
List of Buffer Overflow Cases
Netmeeting 2.x exploit
(http://www.cultdeadcow.com/cDc_files/cDc-351/)
NT RAS Exploit
(http://www.cerberus-infosec.co.uk/wprasbuf.html)
IIS Hack
(http://www.eeye.com)
Oracle Web Exploit
(http://www.cerberus-infosec.co.uk/advowl.html)
Outlook Exploit
(http://www.ussrback.com/labs50.html)
IIS .printer
(http://www.securityfocus.com/bid/2674)
Protection against Buffer Overflows
Buffer overflow vulnerabilities are inherent in code due to poor or no error checking.
General ways of protecting against buffer overflows:
1. Close the port of service
2. apply vendors patch or install the latest version of the software
3. Filter specific traffic at the firewall
4. Test key application
5. Run software at the least privilege required
Summary
Hackers use a variety of means to penetrate systems.
Password guessing / cracking is one of the first steps.
Password sniffing is a preferred eavesdropping tactic.
Vulnerability scanning aids hacker to identify which password cracking technique to use.
Key stroke logging /other spy ware tools are used as they gain entry to systems to keep up the attacks.
Invariably evidence of “having been there and done the damage” is eliminated by attackers.
Stealing files as well as Hiding files are means used to sneak out sensitive information.