Hacktivists have claimed responsibility for taking down the public-facing infrastructure of popular Linux operating system distribution Ubuntu, as well as Canonical, the company that develops and maintains the software. The attack began on Thursday, and affected services that Ubuntu users rely on. “Canonical’s web infrastructure is under a sustained, cross-border attack and we are working to address it. We will provide more information in our official channels as soon as we are able to,” the company said on its website.  The hacktivists are believed to have launched a distributed denial-of-service, or DDoS , a crude but often effective attack that consists of flooding a target with junk traffic until it overloads or crashes.  Ubuntu developers have been discussing the attack on an unofficial Ubuntu community forum, claiming that the attack affects Ubuntu’s security API, and several Ubuntu and Canonical websites.…