The cyberattack that took out many of the internet’s most popular websites Friday is bound to happen again, local security experts say. Friday’s distributed denial of service (DDoS) attack targeted the New Hampshire-based domain name server provider Dyn Inc. Security researchers say it was enabled by insecure Internet of Things devices whose owners failed to change a default password. Infected with the malware Mirai, hundreds of thousands — and potentially millions — of insecure devices ultimately could join this botnet army to create future havoc on the Web. “For Internet of Things, there’s been an explosion in this sector.