An 18-year-old New Jersey man will plead guilty to the January online attacks that took down the Church of Scientology's website, US federal prosecutors said on Friday.

Dmitriy Guzner of Verona, New Jersey, was part of an underground hacking group called 'Anonymous' that has made the church a target of several attacks. He was charged on Friday but has agreed to plead guilty sometime in the next few weeks, the US Department of Justice.

He faces 10 years in prison on computer hacking charges.

The attacks began on January 19 and managed to knock the website offline by hitting it with several bursts of unwanted internet traffic. The attack, known as a distributed denial of service (DDOS) attack, flooded the site with as much as 220Mbps of traffic, according to computer security firm Arbor Networks. That's considered to be a decent-sized DDOS attack and was enough to disable the website temporarily.

Anonymous quickly followed its attacks with a series of YouTube videos, claiming its actions were a response to what it said were efforts by the Church to suppress a video of movie star Tom Cruise professing his admiration for the religion.

"For the good of your followers, for the good of mankind and for our own enjoyment, we shall proceed to expel you from the internet and systematically dismantle the Church of Scientology in its present form," a creepy computerised voice says in one Anonymous video.