>Amazon
I haven't seen it mentioned here yet but many of Amazon's recent acquisitions have their origins in DARPA (see XData project). Their new graph database (used to build large scale network graphs, i.e. connections) called Neptune was acquired from Systap. The Systap (now Blazegraph - https://www.blazegraph.com/) founders work(ed) closely with DARPA and worked with/for the NSA prior to forming their company. There was no press release for this acquisition and zero coverage, not listed on Wikipedia M&A page. I could only find a few mentions like this one: https://news.ycombinator.com/item?id=15810209
Also acquired recently, Sqrrl (https://sqrrl.com/). Their database technology was also used by the NSA & DARPA to help discover "connections" among other things. "Sqrrl Enterprise is the industry-leading Threat Hunting Platform that unites link analysis, machine learning algorithms, and multi-petabyte scalability capabilities into an integrated solution"
https://en.wikipedia.org/wiki/List_of_mergers_and_acquisitions_by_Amazon