Dynamic Analysis with Tracing and Hooking
Go beyond static disassembly: observe a program as it runs using system-call tracing, library tracing, and function hooking to understand real behavior.
Dynamic Analysis with Tracing and Hooking is a free Assembly Language & x86 Low-Level Systems Programming lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Assembly Language & x86 Low-Level Systems Programming learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Static vs Dynamic Analysis
Static analysis inspects a binary without running it (disassembly, strings). Dynamic analysis watches the program while it executes, revealing behavior that only appears at runtime, such as decrypted strings or network calls.
Why Dynamic Analysis Wins
Packed or obfuscated binaries hide their logic from a disassembler. But to actually do anything, the code must eventually run real instructions and make real syscalls — and that is exactly what dynamic tools capture.
System Call Tracing with strace
On Linux, strace logs every system call a process makes. It instantly shows files opened, network connections, and arguments passed to the kernel.
strace -f ./target # follow child processes
strace -e trace=network ./bin # only network syscalls
strace -p 1234 # attach to running PID 1234Reading strace Output
Each line is a syscall with arguments and return value:
openat(AT_FDCWD, "/etc/passwd", O_RDONLY) = 3
This reveals the program read /etc/passwd and got file descriptor 3 — behavior invisible in static text.
Library Call Tracing with ltrace
ltrace traces calls into shared libraries, like strcmp, malloc, or getenv. This is gold for cracking password checks where the comparison happens in libc.
ltrace ./crackme
# strcmp("hunter2", "letmein") = -1Function Hooking
Hooking intercepts a function call to inspect or change arguments and return values. You redirect the original function pointer to your own code, do your work, then optionally call the original.
LD_PRELOAD Interception
On Linux you can override any libc function by exporting a replacement in a preloaded shared object. The loader resolves your symbol first.
export LD_PRELOAD=./myhook.so
./target # calls now route through your hookA Simple Hook in C
This overrides strcmp to log every comparison, then calls the real one via dlsym(RTLD_NEXT, ...).
#define _GNU_SOURCE
#include <stdio.h>
#include <dlfcn.h>
#include <string.h>
int strcmp(const char *a, const char *b) {
int (*real)(const char*, const char*) = dlsym(RTLD_NEXT, "strcmp");
fprintf(stderr, "strcmp: %s vs %s\n", a, b);
return real(a, b);
}Hardware and Software Breakpoints
Dynamic debuggers use breakpoints to pause execution. A software breakpoint replaces a byte with 0xCC (INT 3). A hardware breakpoint uses the CPU debug registers DR0-DR3 and can also trip on memory reads/writes.
Instrumentation Frameworks
For heavy automation, frameworks like Frida and Intel Pin inject instrumentation at runtime. Frida lets you script hooks in JavaScript while the target runs — ideal for mobile and live analysis.
Anti-Debugging Awareness
Malware fights back. It may call ptrace(PTRACE_TRACEME) to detect a debugger, check timing, or scan for 0xCC bytes. Recognizing these checks is part of dynamic reverse engineering.
Quick Check
Test your dynamic-analysis knowledge.
Recap
You learned to analyze running programs:
- Dynamic analysis reveals runtime behavior static tools miss
- strace traces syscalls; ltrace traces library calls
- Hooking via LD_PRELOAD or Frida intercepts function calls
- Breakpoints (INT 3 / debug registers) and anti-debugging tricks shape the work
Frequently asked questions
Is the “Dynamic Analysis with Tracing and Hooking” lesson free?
Yes — the full text of “Dynamic Analysis with Tracing and Hooking” is free to read here on the web, and the Assembly Language & x86 Low-Level Systems Programming course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Assembly Language & x86 Low-Level Systems Programming course, upgrade to CoddyKit PRO.
What will I learn in “Dynamic Analysis with Tracing and Hooking”?
Go beyond static disassembly: observe a program as it runs using system-call tracing, library tracing, and function hooking to understand real behavior. You practise Assembly Language & x86 Low-Level Systems Programming with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Assembly Language & x86 Low-Level Systems Programming?
No prior experience is required. Assembly Language & x86 Low-Level Systems Programming on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Dynamic Analysis with Tracing and Hooking” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Assembly Language & x86 Low-Level Systems Programming lesson?
Yes. Every Assembly Language & x86 Low-Level Systems Programming lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Using GDB for Assembly Debugging
- Introduction to Disassembly Tools
- Basic Reverse Engineering Techniques
- Dynamic Analysis with Tracing and Hooking