WASHINGTON — Brief internet outages this week in Liberia have captured the attention of cybersecurity researchers around the world, who fear the small West African nation has become a testing zone for global hackers.

Punishing digital attacks sent all of Liberia offline for short, intermittent periods, often barely a second. One cybersecurity researcher said the attacks might signal that hackers were preparing a much larger, similar attack in Europe or North America.

The hackers employed a now-free weapon called Mirai, which harnesses thousands of internet-connected devices – such as baby monitors, home routers and closed-circuit cameras – and turns them into zombie digital soldiers in a “botnet” army that fires digital signals and overwhelms servers with traffic, grinding internet service to a halt.

Hackers used the same malicious tool to yoke together 100,000 infected devices for an attack Oct. 21 on a New Hampshire-based internet backbone company, Dyn, that knocked Amazon, Twitter, Netflix, Airbnb, Reddit, Spotify and dozens of other companies offline for part of a day. That crippling attack using the so-called “Internet of Things” signaled a new era of low-cost malicious assaults.

Among the first to highlight the attacks on Liberia was a U.K.-based cybersecurity architect, Kevin Beaumont, who wrote in a blog post: “The attacks are extremely worrying because they suggest a Mirai operator who has enough capacity to seriously impact systems in a nation state.”

The malicious code dubbed Mirai, which means “the future” in Japanese, was released on hacker forums last summer, enabling any hacker to assemble a botnet to conduct attacks.

Thomas Pore of Plixer, a company that helps clients detect suspicious computer activity, warned that the Liberia attack is only an initial salvo.

“Perhaps Liberia is just the testing ground for something larger. If Botnet #14 is ‘weapons testing’ with Liberia, it’s possible that the USA will see a massive sustained outage of over 4 hours before the end of the year,” Pore said.