Ethical Hacking
Module VI
Trojans and Backdoors
Cheat Sheets
Module Objective
Terms of reference for various malicious code
Defining Trojans and backdoors
Understanding the various backdoor genre
Overview of various Trojan tools
Learning effective prevention methods and countermeasures
Overview of Anti-Trojan software
Learning to generate a Trojan program

Trojans and Backdoors
A Trojan horse is:
An unauthorized program contained within a legitimate program. This unauthorized program performs functions unknown (and probably unwanted) by the user.
A legitimate program that has been altered by the placement of unauthorized code within it; this code performs functions unknown (and probably unwanted) by the user.
Any program that appears to perform a desirable and necessary function but that (because of unauthorized code within it that is unknown to the user) performs functions unknown (and definitely unwanted) by the user.
Working of Trojans
Attacker gets access to the trojaned system as the system goes online
By way of the access provided by the trojan attacker can stage attacks of different types.
Various Trojan Genre
Remote Access Trojans
Password Sending Trojans
Keyloggers
Destructive
Denial Of Service (DoS) Attack Trojans
Proxy/Wingate Trojans
FTP Trojans
Software Detection Killers

Modes of Transmission
ICQ
IRC
Attachments
Physical Access
Browser And E-mail Software Bugs
NetBIOS (File Sharing)
Fake Programs
Un-trusted Sites And Freeware Software
Tool: QAZ
It is a companion virus that can spread over the network.
It also has a "backdoor" that will enable a remote user to connect to and control the computer using port 7597.
It may have originally been sent out by email.
Rename notepad to note.com
Modifies the registry key:
HKLMsoftwareMicrosoftWindowsCurrentVersionRun
Hacking Tool:Tini
http://ntsecurity.nu/toolbox/tini
It is a very tiny trojan program which is only 3 kb and programmed in assembly language. It takes minimal bandwidth to get on victim`s computer and takes small disk space.
Tini only listens on port 7777 and runs a command prompt when someone attaches to this port. The port number is fixed and cannot be customized. This makes it easier for a victim system to detect by scanning for port 7777.
From a tini client you can telnet to tini server at port 7777
Tool: Netcat
Outbound or inbound connections, TCP or UDP, to or from any ports
Ability to use any local source port
Ability to use any locally-configured network source address
Built-in port-scanning capabilities, with randomizer
Built-in loose source-routing capability

Tool: Donald Dick
Donald Dick is a tool that enables a user to control another computer over a network.
It uses a client server architecture with the server residing on the victim`s computer.
The attacker uses the client to send command through TCP or SPX to the victim listening on a pre defined port.
Donald Dick uses default port either 23476 or 23477
Tool: SubSeven
SubSeven is a backdoor program that enables others to gain full access to Windows 9x systems through network connection.
The program consists of three different components : Client (SubSeven.exe), Server (Server.exe) and a Server configuration utility (EditServer.exe).
The client is a GUI used to connect to server through a network or internet connection.
BO2K has stealth capabilities, it will not show up on the task list and runs completely in hidden mode.

Back Orifice accounts for highest number of infestations on Microsoft computers.
The BO2K server code is only 100KB. The client program is 500KB.
Once installed on a victim PC or server machine, BO2K gives the attacker complete control of the system.
Tool: Back Oriffice 2000
Back Oriffice Plug-ins
BO2K functionality can be extended using BO plug-ins.
BOPeep (Complete remote control snap in)
Encryption (Encrypts the data sent between the BO2K GUI and the server)
BOSOCK32 (Provides stealth capabilities by using ICMP instead of TCP UDP)
STCPIO (Provides encrypted flow control between the GUI and the server, making the traffic more difficult to detect on the network)
Tool: NetBus
Wrappers
How does an attacker get BO2K or any trojan installed on the victim`s computer? Answer: Using Wrappers
A wrapper attaches a given EXE application (such as games or orifice application) to the BO2K executable.
The two programs are wrapped together into a single file. When the user runs the wrapped EXE, it first installs BO2K and then runs the wrapped application.
The user only sees the latter application.
One can send a birthday greeting which will install BO2K as the user watches a birthday cake dancing across the screen.
Tool: Graffiti.exe
Hacking Tool: Silk Rope
http://www.h2ohackerz.co.uk/index2.htm
Silk Rope is a wrapper program and has an easy to use user-interface.
Silk Rope binds BO installer with a program of your choosing, saving the result as a single file.
Presently, the icon is the generic single-file-install icon (an opening box with a window in the background), you can change it with an icon utility such as Microangelo.
Tool: EliteWrap
http://homepage.ntlworld.com/chawmp/elitewrap/
EliteWrap is an advanced EXE wrapper for Windows 95/98/2K/NT used for SFX archiving and secretly installing and running programs.
With EliteWrap one can create a setup program that would extract files to a directory and execute programs or batch files to display help, copy files, etc.

Tool: IconPlus
IconPlus can be used to change icons in EXE files

Tool: Restorator
Packaging Tool: WordPad
When you place a CD in your CD-ROM drive, it automatically starts with some set up interface. An Autorun.inf file that is placed on such CD`s is responsible for this action which would look like this:
[autorun]
open=setup.exe
icon=setup.exe
Therefore it is quite possible that while running the real setup program a trojan could be run very easily.
Turn off the Auto-Start functionality by doing the following:
Start button-> Settings-> Control Panel-> System-> Device Manager-> CDROM-> Properties -> Settings
Infecting via CD-ROM
Hacking Tool: Whack-A-Mole
Popular delivery vehicle for NetBus/BO servers is a game called Whack-A-Mole which is a single executable called whackamole.exe
Whack-A-Mole installs the NetBus/BO server and starts the program at every reboot.
BoSniffer
Soon after BO appeared, a category of cleaners emerged, claiming to be able to detect and remove BO.
BOSniffer turned out to be one such Trojan that in reality installed Back Orifice under the pretext of detecting and removing it.
Moreover, it would announce itself on the IRC channel #BO_OWNED with a random username.
Hacking Tool: Firekiller 2000
FireKiller 2000 will kill (if executed) any resistant protection software.
For instance, if you have Norton Anti-virus auto scan in your taskbar, and ATGuard Firewall activated, this program will KILL both on execution, and makes the installations of both UNUSABLE on the hard drive; which would require re-installation to restore.
It works with all major protection software like AtGuard, Conseal, Norton Anti-Virus, McAfee Anti-Virus etc.
Tip: Use it with an exe binder to bind it to a trojan before binding this file (trojan and firekiller 2000) to some other dropper.

ICMP Tunneling
Covert Channels are methods in which an attacker can hide the data in a protocol that is undetectable.
Covert Channels rely on techniques called tunneling, which allows one protocol to be carried over another protocol.
ICMP tunneling is a method of using ICMP echo-request and echo-reply as a carrier of any payload an attacker may wish to use, in an attempt to stealthily access, or control a compromised system.
Hacking Tool: Loki
(www.phrack.com)
Loki was written by daemon9 to provide shell access over ICMP making it much more difficult to detect than TCP or UDP based backdoors.
As far as the network is concerned, a series of ICMP packets are shot back and forth: Ping, Pong-response. As far as the attacker is concerned, commands can be typed into the loki client and executed on the server.
Loki Countermeasures
Configure your firewall to block ICMP incoming and outgoing echo packets.
Blocking ICMP will disable ping request and may cause inconvenience to users.
So you need to carefully decide on security Vs convenience.
Loki also has the option to run over UDP port 53 (DNS queries and responses.)

Reverse WWW Shell - Covert channels using HTTP
Reverse WWW shell allows an attacker to access a machine on your internal network from the outside.
The attacker must install a simple trojan program on a machine in your network, the Reverse WWW shell server.
On a regular basis, usually 60 seconds, the internal server will try to access the external master system to pick up commands.
If the attacker has typed something into the master system, this command is retrieved and executed on the internal system.
Reverse WWW shell uses standard http protocol.
It looks like internal agent is browsing the web.
Backdoor Countermeasures
Most commercial ant-virus products can automatically scan and detect backdoor programs before they can cause damage (Eg. before accessing a floppy, running exe or downloading mail)
An inexpensive tool called Cleaner (http://www.moosoft.com/cleanet.html) can identify and eradicate 1000 types of backdoor programs and trojans.
Educate your users not to install applications downloaded from the internet and e-mail attachments.
Tool: fPort
Tool: TCPView
Process Viewer
Inzider - Tracks Processes and Ports
http://ntsecurity.nu/cgi-bin/download/inzider.exe.pl
This is a very useful tool that lists processes in your Windows system and the ports each one listen on.
For instance, under Windows NT/2K, BO2K injects itself into other processes, so it is not visible in the Task Manager as a separate process.
When you run Inzider, you will see the port BO2K has bound in its host process

Hacking Tool: Senna Spy
http://sennaspy.cjb.net/
Senna Spy Generator 2.0 is a trojan generator. Senna Spy Generator is able to create a Visual Basic source code for a trojan based on a few options.
This trojan is compiled from generated source code, anything could be changed in it.
Hacking Tool: Hard Disk Killer (HDKP4.0)
http://www.hackology.com/programs/hdkp/ginfo.shtml
The Hard Drive Killer Pro series of programs offer one the ability to fully and permanently destroy all data on any given Dos or Win3.x/9x/NT/2000 based system. In other words 90% of the PCs worldwide.
The program, once executed, will start eating up the hard drive, and or infect and reboot the hard drive within a few seconds.
After rebooting, all hard drives attached to the system would be formatter (in an un recoverable manner) within only 1 to 2 seconds, regardless of the size of the hard drive.
System File Verification
Windows 2000 introduced Windows File Protection (WFP) which protects system files that were installed by Windows 2000 setup program from being overwritten.
The hashes in this file could be compared with the SHA-1 hashes of the current system files to verify their integrity against the `factory originals‘
sigVerif.exe utility can perform this verification process.
Tool: Tripwire
Tripwire will automatically calculate cryptographic hashes of all key system files or any file that you want to monitor for modifications.
Tripwire software works by creating a baseline “snapshot” of the system
It will periodically scan those files, recalculate the information, and see if any of the information has changed. If there is a change an alarm is raised.

Tool: Beast
Beast is a powerful Remote Administration Tool (AKA trojan) built with Delphi 7.
One of the distinct features of the Beast is that is an all-in-one trojan (client, server and server editor are stored in the same application).
An important feature of the server is that is using the injecting technology.
Summary
Trojans are malicious pieces of code that carry cracker software to a target system
Trojans are used primarily to gain and retain access on the target system
Trojans often reside deep in the system and make registry changes that allow it to meet its purpose as a remote administration tool
Popular Trojans include back orifice, netbus, subseven, beast etc.
Awareness and preventive measures are the best defense against Trojans.