Memcrash DDoS exploits used for extortion.
Memcrash distributed denial-of-service attacks have been criminalized, as DDoS attackers extort cryptocurrency from victims (eSentire). Akamai researchers who've followed the DDoS campaigns closely (and played a major role in GitHub's swift recovery from what's been called the largest DDoS attack on record) spotted extortion notes buried in the attack traffic. The criminals are asking for Monero, attractive to them because of its greater anonymity relative to competing cryptocurrencies like Bitcoin (Mashable).
In addition to the well-known attack on GitHub, a partial list of other victims includes Google, the National Rifle Association, PlayStation Network, Amazon, and Kaspersky (HackRead).