The Korean NIS (National Intelligence Service) has published an online game to help you spot North Korean spies.
It includes things like people covering their mouths with their hands when they talk (holy crap! every Korean woman with a cellphone is a North Korean spy!)
People who bring weapons to protests, people who leave PC rooms quickly after posting "impure" articles, and people who wear "I love Kim Il-sung" pins are among suspects for North Korean Spy-iness.
What about people who raise funds to buy weapons to assault the police?
And don't forget, if you see a person wearing a Kim Il Sung t-shirt, talking with his hand over his mouth as he grabs his stick and furtively leaves the PC Room after posting messages to corrupt Korea's youth, and heads for a protest to hand out tracts and incite violence while photographing sensitive government compounds, the number to call is 111: Korea's spy hotline.