This paper performs an in-depth analysis of identified high frequency traders in the KOPSI200 futures market. Although high frequency traders’ order submission distribution across order aggressiveness is quite similar to other algorithmic traders and ordinary traders, 94 percent of non-marketable limit orders by high frequency traders are revised or cancelled and 74 percent of participation in trades is through marketable orders. This paper documents that this highly impatient behavior is attributed to trading strategies that are based on extremely short-lived private information about future price movements, not passive market-making. Limit order revisions exhibit a tag-along effect; when the market moves away from (approaches) the original limit price, the revision price is set more (less) aggressively. Active use of fleeting orders by high frequency traders reduces the information content of the limit order book.