Screenshot by Laura Hautala/CNET

Hacktivist group Anonymous declared "total war" on Donald Trump, urging hackers to knock the billionaire's websites offline as it put the Republican front-runner in its sights for the second time.

In a video posted Tuesday, a representative of the group called on hackers to attack Trump's websites and reveal any personal information about the candidate they unearth. It also addressed Trump directly.

"Your inconsistent and hateful campaign has not only shocked the United States of America, you have shocked the entire planet with your appalling actions and ideas," said a figure in the YouTube video, wearing the Guy Fawkes masked favored by members of Anonymous. The YouTube poster didn't respond to a message sent via Twitter.

The call to attack Trump's online presence marks the second time Anonymous has targeted the developer and reality television star. In December, the loose network of hackers and Internet activists appeared to take down the website of the candidate's eponymous building, New York's Trump Tower.

The attackers used a distributed denial of service attack, a relatively common and simple hack. DDoS attacks work by overloading the back end of websites and knocking them offline. The attacks are generally used to make a point rather than cause permanent damage.

"They're extremely easy and extremely inexpensive," said Ben Desjardins, who specializes in preventing DDoS attacks for cybersecurity company Radware. Radware worked with Boston Children's Hospital when it was the target of an Anonymous attack in 2014.

The Anonymous video includes portions of now-famous clips in which Trump calls Mexican immigrants rapists and faces off with Megyn Kelly at a Fox News debate. It concludes by calling for hackers to take down a website for Chicago-based Trump Towers on April 1.

The hashtag #OpTrump, originally brought out in the first Anonymous video declaring Trump a target, picked up steam again on Tuesday. Some Twitter users cheered on Anonymous and others debated the usefulness of their campaign.

"I am so excited for the shenanigans to commence!" said Twitter user @daronammo.

"#OpTrump will have to do better than sharing the things Trump says in private if the things he says in public aren't dissuading his voters," said Twitter user @DaggsyD.

Trump's voice mail was hacked earlier this month, according Gawker, which released transcripts of phone messages left by national media figures the publication described as cozy.

Anonymous has caused headaches for its targets in the past. It attacked the Westboro Baptist Church, a small religious group known for protesting soldiers' funerals. It also claimed to out high-profile members of the Ku Klux Klan and take down Web accounts run by ISIS.