MongoDB has been in the news for hackers deleting unsecured databases and demanding money to return the data.
Now copycats are starting to look at other targets too like the thousands of unsecured Cassandra databases. Preventing this is very simple: don't allow Cassandra to listen on public interfaces. Of course additional security measures are useful as defense in depth, but bottom line if the bad guys can't connect to your cluster they can't harm it. -- Jonathan Ellis co-founder, http://www.datastax.com @spyced
