(CNN) -- Computer hackers supporting WikiLeaks shifted targets Thursday from Amazon to PayPal, they said, as Dutch authorities announced an arrest in connection with hacker attacks on the websites of MasterCard and Visa.
The Dutch High Tech Crimes unit arrested a 16-year-old in The Hague, Netherlands, with prosecutors saying he confessed to attacks on the websites.
"He is probably part of a larger group of hackers, who are under continued investigation," they said. The teen is due in court Friday in Rotterdam.
Separately, a group of hackers calling themselves Anonymous Operations said they would attack PayPal, not Amazon.com, about an hour after an attack on Amazon was due to start.
"We can not attack Amazon, currently. The previous schedule was to do so, but we don't have enough forces," they said on Twitter.
Anonymous Operations released a do-it-yourself hacking tool earlier Thursday so supporters could make their own computers part of the attack.
The Amazon.com attack was supposed to have started at about 11 a.m. ET.
So far, PayPal appears to be operating normally. The site has been attacked, which has slowed it down but has "not significantly impacted payments," PayPayl's Anuj Nayar told CNN.
Amazon.com has massive server capacity -- much more than that of Mastercard or Visa -- in order to handle the holiday e-commerce rush. Its server infrastructure ensures that a massive traffic spike can't take site down, whether it comes from a hacker-led attack or genuine shoppers.
Anonymous Operations released the hacking tool on Twitter and called for followers to translate it into other languages.
Hackers have been targeting websites of organizations they see as hostile to WikiLeaks and its Editor-in-Chief Julian Assange, who was arrested in London this week on allegations unconnected to the website's publication of secret documents.
Amazon used to host WikiLeaks' website in the United States, but shut it down last week, saying it had violated their terms of service by publishing material it did not own and which could cause harm.
PayPal stopped handling donations to WikiLeaks last week.
The United Nations Commissioner for Human Rights said Thursday that pressure on websites to cut off WikiLeaks could violate the site's right to freedom of expression.
"I'm concerned about reports of pressure exerted on private companies, including banks, credit card companies, to close down credit lines for donations to WikiLeaks as well as to stop hosting the website or its mirror sites," Navi Pillay said in Geneva, Switzerland
"They could be interpreted as an attempt to censor the publication of information," she said at a press conference. "If WikiLeaks has committed any recognizable illegal acts, then this should be handled through the legal system and not through pressure and intimidation including on third parties."
Anonymous Operations members told CNN Thursday their goal was "freedom of information. Any and all information."
They were originally focused on piracy, but shifted their attention to WikiLeaks because it was "obvious we had to help."
"While their methods may be controversial, they do demand transparency, which is something we definitely support," they said, adding that once they feel they have made their point about WikiLeaks, they will go back to fighting for "unlimited freedom of expression."
They spoke to CNN Correspondent Atika Shubert in an online chat after being contacted through Twitter.
WikiLeaks said Thursday it was not associated with Anonymous Operations and neither supported nor condemned their actions.
"This group is not affiliated with WikiLeaks. There has been no contact between any WikiLeaks staffer and anyone at Anonymous. WikiLeaks has not received any prior notice of any of Anonymous' actions," it said on its website.
"We neither condemn nor applaud these attacks. We believe they are a reflection of public opinion on the actions of the targets," WikiLeaks spokesman Kristinn Hrafnsson said.
The hackers have been attacking sites with a relatively simple tool called a low orbit ion cannon (LOIC).
Users who put it on their computer are allowing Anonymous Operations to use the machine to launch attacks on a chosen target, computer security expert Mikko Hypponen told CNN.
He hasn't seen any obvious code in the tool that would allow Anonymous Operations to use people's computers for other purposes, he said.
Because people cut and paste the code off a website, rather than downloading it, there's no way to tell how many people have put the tool on their computers.
One person who put the hacking tool on his computer told CNN it was the arrest of Assange that "sparked this global movement.
"If he was not arrested, I doubt that the movement would have grown to its current unstoppable size," said the computer user, who refused to give his name but said he was not a hacker.
The website of the lawyer representing the women who accuse Assange of sex attacks in Sweden went down on Thursday, said the office of the lawyer, Claes Borgstrom.
The Swedish Prosecution Authority's website was down earlier in the week. Anonymous Operations told CNN it had carried out that attack.
The Swedish newspaper Aftonbladet reported that government's website also went down for a few hours, but the government refused to comment, saying it did not discuss security matters.
And a website has been set up in the name of Swedish Justice Minister Beatrice Ask -- but it automatically redirects users to WikiLeaks.
WikiLeaks founder Assange is being held in a London jail as the British courts decide whether to extradite him to Sweden to face questioning. He has not been charged with a crime.
CNN's Francesca Church, Nicola Hughes, David DeSola, Richard Allen Greene, Per Nyberg, Robyn Turner, Julianne Pepitone and Amir Ahmed contributed to this report.