Over the past month there have been a number of Distributed Denial of Service (DDoS) attacks on cryptocurrency-related businesses around the world, in particular exchanges, who have received extortion letters demanding bitcoin payment to stop the attacks.

In the past 24 hours there have been DDoS attacks on the bitcoin exchange Kraken and multi-currency exchange Cryptsy. Since the attacks started, Kraken has managed to restore service to normal; however, at the time of writing, Cryptsy is still offline, although messages on twitter say mitigation work is underway. Companies targeted have, naturally, declined to give in to the extortion attempts to prevent themselves becoming even bigger targets in the future.

The site is under DDoS at the moment. Extortion letter received. Obviously, not paying. Please bear with us. — Kraken Exchange (@krakenfx) November 24, 2015

I don't know what's worse–the DDoS or all the crazy ambulance chaser DDoS protection service spammers. Systems back to normal now. — Kraken Exchange (@krakenfx) November 25, 2015

Website offline due to denial of service attack. We are working to mitigate. — BigVern (@cryptsy) November 25, 2015

Bitcoin exchanges are not the only ones being targeted either, both CryptoCoinsNews and Hacked were targeted in the past few days, with CCN posting a screenshot of the e-mail demanding 2 bitcoins to stop the attack, rising to 3 if their demands weren’t met within a day. In response, CCN has posted all the details of the attack it has and offered a reward of five bitcoins to anyone able to help identify the perpetrators whereby the information leads to a successful police report. Maybe those responsible should hand themselves in, after all, it’s a bigger reward!