Cybersecurity is red-hot for investors — here's what Duo, Splunk, Tanium and the rest of those companies actually do

Cisco announced on Thursday that it would acquire Duo Security, a company that specializes in products that help companies manage identity and secure access to devices, for $2.35 billion.

Cisco's move makes sense. One of the most pressing issues in cybersecurity today is how to authenticate users, or prove that they are who they claim to be. It's the problem that leads to some of the cybercrimes most expensive to business -- like email compromise, wire fraud and theft of valuable intellectual property. It's also at the root of the attacks suffered by the Democratic National Committee in the 2016 election.