The high transaction speed, lack of traceability, and multi-national nature of cryptocurrencies make them prime targets for small-time thieves and well-financed attackers alike. As such, cryptocurrency exchanges continually face a barrage of website/API attacks, sophisticated takeover attacks of their customers' accounts, malicious code embedded in 3rd-party software components, and security attacks on the underlying cryptocurrencies. This presentation discusses these attacks and the novel defenses that exchanges are implementing.