I'm Warren Jonhow Lee, a System Architect, Hacker.
I've built Chartmetric & PttBrain from the ground up.
Currently working @ Parabola
Recently I have been playing around with couple essential design patterns and want to write down my thoughts and compare them. The two patterns ( and ) are similar but not identical. Let's talk…
Let's Talk About DNS Resolver First From the wiki page of DNS Server A DNS server is a computer server that contains a database of public IP addresses and their associated hostnames, and in most…
It Began with a Sad Story I wrote this article to memorize a lesson I've learned due to my stupidity. The store was, two weeks ago I tried to transfer my domain (pttbrain.com) registrar from GoDaddy…
This page shows how PTT categorizes boards (you can click and play with that !!). alt text Also you can see the number of live use count after the board name. This page contains fascinating…
Have been working with Docker things for couple months. Can't wait to share some amazing things people can do with Docker container. What is container ? Well, from the official docker documentation…
CTF time !! Let's find flags. alt text Hidden Page ~ 🚩(1/7) Log in to the app using a newly created account, we can see home page like alt text Clicking two posts below, we can see their URLs http…
Let's discuss one of my favorite DP problem. alt text Given weights and values of n items, put these items in a knapsack of capacity W to get the maximum total value in the knapsack. In other…
CTF time !! Let's find flags. alt text PHP File Inclusion Vulnerability ~ 🚩(1/3) Simply by giving the input text (under 'Add comment' text area) Then we are able to do remote php code execution…
CTF time !! Let's find flags. alt text SQL Injection ~ 🚩(1/3) Let's navigate to /login route (by clicking "Create a new page") alt text By giving username ' (single quote), we got an error page Focus…
Below is the shortest summary about web scraping Web scraping is the process of using bots to extract content and data from a website. (https://www.incapsula.com) Basically, there are two kind of…
Before jumping into the PttBrain product, I would like to talk about what PTT is a little bit. About PTT PTT Bulletin Board System, is the largest terminal-based bulletin board system (BBS) based in…
In general, there are two types of network scan. Passive Scan (Whireshark, ARP Tables) Active Scan (Hping, NMAP, Scapy...etc) The difference between two is passive scan will not be recognized by…
Buffer overflows is one of most common bugs in C/C++ programs. Let's talk about some common buffer overflows. Stack Smashing What are buffer overflows ? Consider the web server contains a function…
To list some basic ciphers One Time Pad Key has the same length, or longer than, the message being sent. Its secure against one-time ciphertext-only attack. (Shannon, 1949) Stream Cipher OTP key is…
alt text Today I received an interesting phishing email. I did the research and found out it's actually a good learning opportunity, since attacker's server demonstrates excellent practice in network…