"Where traditional databases hit their limits, Hadoop starts to emerge as a much better fit for solving unique analytics challenges," Lockner says. "Because data can be incorporated from multiple sources with varying types of data structures, Hadoop enables more analysis across multiple data feeds in a single platform -- solving some of the toughest data integration challenges commonly associated with relational data warehouse architecture."
The article doesn't provide details about what type of data they working with, it's only described as being more or less unstructured, originating from multiple sources, and being analyzed for security purposes. If I had to guess, they are probably using Hadoop as a staging environment to injest things like emails or web forum posts and searching for keywords and phrases that would indicate security threats. For example, there are websites where hackers go to trade or sell account numbers, logins, and other personal information.
It makes sense to do this sort of document archiving and semantic data crunching outside the relational database.
"Do not seek to follow in the footsteps of the wise. Instead, seek what they sought." - Matsuo Basho