An activist group working to end China's Internet censorship is facing an ongoing distributed denial of service (DDoS) attack that threatens to cripples its activities.
GreatFire.org, a censorship watchdog based within the country, reported on Thursday that it had been hit with its first DDoS attack.
Although it's not known who is behind the attack, China has been suspected of using the tactic before to take down activist websites.
DDoS attacks work by using an army of hacked computers to send an overwhelming amount of traffic to a website, effectively disabling it.
In an Internet posting, GreatFire said that it was seeing 2.6 billion requests per hour, and that its websites had been forced offline.
"We are not equipped to handle a DDoS attack of this magnitude and we need help," the group added.
The DDoS attack is targeting mirror websites GreatFire created to let Chinese users access blocked content, such as Google, BBC, the New York Times and other sites known to offer articles critical of the Chinese government.
To create the mirror websites, GreatFire has been using Amazon.com to host them through its cloud services. If the country wanted to cut access to the sites, the government would have to cause "collateral damage" and risk blocking Amazon servers that also support a large number of businesses, according to the group.
GreatFire suspects that the DDoS is in response to a Wall Street Journal article about the group's use of cloud services to poke holes through China's censorship.
"Because of the number of requests we are receiving, our bandwidth costs have shot up to US$30,000 per day," the group said. "Amazon, which is the service we are using, has not yet confirmed whether they will forgo this."
Amazon did not immediately respond to a request for comment on Thursday.
GreatFire, which is run by an anonymous team, has said the bandwidth costs will "put a significant squeeze" on its operations. The group is asking the public to contact Amazon about supporting GreatFire's cause.
As for China, the country has always denied carrying out state-sponsored hacking attacks. But in January, authorities blasted GreatFire for alleging that it had launched a cyberattack against Microsoft's Outlook.com. "This is unprovoked speculation, and purely amounts to disinformation and slander from anti-China forces based abroad," a government office said at the time.
The office went on to claim that GreatFire had launched unprovoked attacks against the Chinese government, and that it was seeking to incite unrest.