How did the Israeli pull off the AR-924 Pager Attack against Hezbollah? – Hackers perspective.

When working with devices, the only real way to hack a small device is to use special tools and specific electrical engineering knowledge to pull this off. I have very little knowledge of electrical engineering but did mess with it in the 90’s when I was hacking DirecTV and the H Cards to get free cable.

I am “somewhat” familiar with the assembly language concepts and processes that could be used to create custom commands for pagers when a certain text is received. Pagers typically use POCSAG (Post Office Code Standardization Advisory Group) protocol for message transmission, and the assembly code you would need would interact with this communication protocol at a low level, allowing specific actions to be triggered when a particular message arrives.

To implement a command based on a received text message, you would typically follow these steps:

1. Receive and Parse the Message

• The pager continuously listens for incoming messages. In assembly, you would write routines to decode the POCSAG signal, which includes identifying the specific “capcode” (the unique identifier for the pager) and decoding the message content.
• A common assembly operation here would be to compare the incoming text to predefined strings or patterns using string comparison instructions.

2. Match the Message

• Once the text message is received and stored in memory, you would use a comparison algorithm (usually something like CMP in assembly) to check if the text matches a specific keyword or command.
  • For example, if the text message contains the word “ALERT,” the assembly routine would match this and trigger a specific function such as running a voltage to a specific component on the PCB, which can trigger a blasting cap.

3. Execute Command

• After matching the message, you would invoke specific commands. In assembly, this could involve setting certain registers to predefined values and calling subroutines (using the CALL or JMP instruction).
• The command could trigger a buzzer, display a certain message on the screen, or perform an external action such as sending a response.

Requirements:

• Knowledge of Electrical Engineering
• Assembly Language
• Multimeter Tools
• Oscilloscope/Logic Analyzer

To edit the assembly code on a pager’s PCB or components, you will need specific hardware, software, and technical information about the pager’s microcontroller and programming interface. Here’s what you typically need:

1. Microcontroller Information

You need to identify the microcontroller (MCU) used in the pager, as different MCUs have different architectures and instruction sets. The microcontroller datasheet is critical for understanding the pinouts, memory structure, registers, and the assembly language required for programming.

• Datasheet: Look for information on the exact model of the microcontroller used in the pager. It will give you details on how to communicate with the device and program it.
• Instruction Set: Each microcontroller has its own assembly language, which you’ll need to write or modify.

2. Firmware Access

Pagers usually run on embedded firmware. To edit assembly code on the PCB, you’ll need access to the pager’s firmware.

• Firmware Dump: You may need to extract the current firmware from the microcontroller using specialized hardware tools (discussed below).
• Decompiling: If the firmware is compiled, you might need to decompile it into assembly code using tools like Ghidra or IDA Pro, which allow for reverse engineering of machine code back into assembly.

3. Programming Tools

You need the proper hardware and software tools to communicate with the microcontroller on the PCB and upload modified code.

• In-System Programmer (ISP) or JTAG Interface: These are standard debugging and programming interfaces used to interact with microcontrollers. They allow you to read/write to the flash memory where the firmware is stored.
  • Common programmers: USBasp for AVR MCUs, ST-LINK for STM32 microcontrollers, or Pickit for PIC microcontrollers.
  • For some MCUs, you might need proprietary tools from the manufacturer.
• Development Environment (IDE): You’ll need an assembler and possibly a development environment depending on the MCU you’re working with. Many manufacturers provide IDEs that include an assembler, simulator, and a way to upload code to the device (e.g., AVR Studio for Atmel MCUs, Keil for ARM-based devices).
• Disassembler/Debugger: If you are working with an existing firmware and want to modify its behavior, tools like Ghidra, IDA Pro, or Radare2 allow you to view the assembly code of the existing program. You can step through the code and understand its logic before making changes.

4. Programming the Pager

Once you have written or modified the assembly code, you’ll need to upload it to the pager’s microcontroller.

• Burning the Code: You would use your ISP or JTAG tool to upload the modified firmware to the pager’s microcontroller.
• Testing: After the upload, you’ll need to verify the code changes by testing the pager’s functionality. This can be done by sending a specific message to the pager and observing if the programmed response (e.g., a certain command) is executed.

5. Hardware Setup

In some cases, you may need to directly interface with certain components on the PCB for testing or debugging.

• Oscilloscope/Logic Analyzer: To ensure proper communication with the microcontroller or to monitor the behavior of specific pins (e.g., data lines for incoming messages).
• Multimeter: To verify voltage levels, check connections, and ensure proper electrical operation on the PCB.

6. Component Modification (if needed)

If you’re making more extensive modifications, such as changing how the pager handles signals or power, you might need to modify components (e.g., adding resistors or capacitors, or replacing the crystal oscillator for clock timing).

Example Process for Editing Code:

1. Identify the microcontroller used in the pager (using the datasheet).
2. Extract firmware using a programmer.
3. Decompile the firmware to assembly code (if necessary) and analyze it.
4. Modify the code to trigger certain actions when specific messages are received.
5. Assemble and recompile the code.
6. Flash the modified firmware back to the pager using an ISP or JTAG interface.
7. Test the pager to ensure the desired functionality works.

Additional Resources:

• Microcontroller datasheets and development kits: Most microcontroller manufacturers like Atmel, Microchip, or STM provide detailed development environments and datasheets.
• Reverse engineering tools: Ghidra, IDA Pro, and other disassemblers can help you inspect and modify the existing firmware.

I have yet to be able to find the AR-924 Pager Schematics but I am in the process of ordering the actual device if I am able to find it to test my theory.