Its been 4 days already that Bitcoin is in below $15k, it started to drop on 21st of December 2017. It drops nearly 40% from $20k down to $12.5k in just a few days ago. There are so many speculations arises on why this huge drop happened. So many factors affecting this incident such as the bitcoin cash theory, investors prefer more on altcoins, the pump and dump theory & etc. But I think the main reason why this drop happened is the incident happened in South Korea.
The South Korean cryptocurrency exchange Youbit was hacked and lost 17% of their total holdings including their user's online wallets. This is the second time that they were hacked, they lost nearly 4,000 Bitcoins last April cyber attack. Immediately, Youbit filed for bankruptcy and they're saying that the remaining 75% of user funds will eventually be available and they'll try to get back the next 75%. Speculations spread throughout the web that the possible culprit of the hacking incident was the North Korea behind the attack and South Korean government still investigating this matter. This incident will surely raise a red flag for all virtual currency investors to be very careful on their hard-earned currency. Exchanges are still weak and subject to hacking and these will scare-off a lot of investors. We must secure our coins and keep it from hackers, if possible we will store it in an external storage - The World of Cryptocurrency - Security