Forget weapons of mass destruction—could the gravest threat facing national security be a weapon of mass disruption?

Last Friday, hackers targeted a New Hampshire company called Dyn, leaving major websites like Twitter, Reddit, and more unreachable to users through the late afternoon.

How is that possible? Dyn offers "Domain Name System" services, which connect web addresses to the servers that content is actually hosted on, so users can access it. Homeland security expert Juliette Kayyemjoined Boston Public Radio to explain in plain English.

"It's essentially what's described as the phonebook of the internet. It holds the capacity to make the internet move for a lot of big companies like Twitter, as we saw, Netflix, and others," she said.

Hackers bombard companies like Dyn with fake requests, which overwhelm the system. 

"It suffered what can only be described as an epic Denial of Service attacks that were probably targeted against a specific individual," Kayyem said. "It brought the whole system down."

Kayyem said that the fact that single companies are responsible for handling such an important element of internet usage opens the whole system up to vulnerabilities. 

"[The attack] was unprecedented, but it's just the first in kind, because we have so much information in a single point of entry like one of these companies, and it's really hard to completely protect them," Kayyem said.

The breach, she continued, has implications for the country's cybersecurity. 

"It has a national security implication, which is: if our grid can't sustain a private sector attack on an individual in New Hampshire and major services go down, imagine something much more coordinated," she said.

To hear more from homeland security expert Juliette Kayyem, tune in to Boston Public Radio above.