Bitcoin, the world’s most popular cryptocurrency, hit an all-time high of $17,428.42 on Tuesday. Experts say bitcoin appears destined to soon break the $20,000 mark. The massive rise in value and hype has brought hackers, scammers and other criminals calling. Security firm Imperva reports that from July to September, DDoS attacks against cryptocurrency exchanges increased. Last month, warnings surfaced that software for wallets tied to a new cryptocurrency called “bitcoin gold” had been hacked.”]