He received his PhD in industrial and systems engineering from Korea Advanced Institute of Science and Technology (KAIST) in 2009. He received an MS degree in industrial engineering from KAIST in 2000. He received a BS degree in industrial management from KAIST in 1998.

He founded A3 Security Consulting, the first information security consulting company in South Korea in 1999. Also, he was a member and the last leader of KUS (KAIST UNIX Society), the legendary hacking group in South Korea. Currently he is a professor in School of Cybersecurity, Korea University. His recent research is focused on detecting intrusions or abnormal activities in online games, automobile, and various payment systems. Before joining Korea University, he was a technical director (TD) and a head of information security department of NCSOFT (2004-2010), one of the most famous MMORPG companies in the world.