A sustained distributed denial of service attack against 4chan has kept the site's message boards mostly offline since the weekend:
4chan's status page, which is hosted on Google's Blogger platform, announced on Sunday 13 November that the site was down due to a large DDoS attack. 4chan today revealed that the ongoing DDoS attack consists of a UDP packet flood on port 80. Such attacks typically aim to disrupt normal operation of a website, either by saturating all available bandwidth, or by exhausting the processing capacity of a web server, thus denying service to legitimate users.
The attack also affected 4chan's main page at www.4chan.org, which has been intermittently unavailable during the same period:
Many popular internet memes are believed to have originated from 4chan's message boards, including Lolcats and the practice of rickrolling. The boards were also used to recruit volunteers when the group Anonymous carried out a series of DDoS attacks against MasterCard, Visa and PayPal last year. When 4chan itself subsequently suffered a similar attack at the start of this year, 4chan made light of the fact that it had joined "the ranks of MasterCard, Visa, PayPal et al.–an exclusive club!".