Often this involves arbitrage, where one asset has two different prices on separate exchanges. If, for instance, you can buy an asset for $10 on one exchange and nearly instantly sell it for $10.25 on another, you will have essentially secured a riskless profit. Doing so over and over can be highly profitable. Some of the more well-known names in HFT are Jump Trading, Citadel Securities, Virtu and Hudson River Trading.
