Anonymous strikes again. Fresh off the last few days’ worth of Web attacks, designed as a kind of cyber-retribution for the demise of file-sharing site Megaupload at the hands of the FBI, members of the “hacktivist” group have taken to Twitter to claim accountability for an attack on CBS.com this morning. And by CBS.com, we mean all of CBS.com. As in, the attackers didn’t just force the site offline using a barrage of distributed denial-of-service attacks (DDOS) delivered by the group’s “Low Orbit Ion Cannon” tool – which has now been transformed into a Web-based attack vector that unsuspecting users can unknowingly participate in. It was first assumed that Anonymous somehow acquired root access to CBS.com in this morning’s attack, as the site’s files and directories appeared to have been wiped. However, additional investigation reveals that the attackers used a technique called DNS poisoning to redirect visitors to different web servers than those hosting CBS’ site. “Anonymous did not take down #CBS .com ; the IP for their web host changed from 220.127.116.11 to 18.104.22.168 & 37; looks like poisoned DNS,” wrote Twitter user @jeremiahfelt. Users attempting to access the main CBS index page were instead shown a directory structure containing just one file – foundry.html. Any attempts to access any of CBS.com’s sub-sites, like bookmarked pages for its litany of television shows, for example, were met with 404 Not Found errors. According to the Twitter account @youranonnews, CBS.com was offline for approximately 20 minutes. But CBS hasn’t been Anonymous’ only Sunday target. The primary site for Universal Music was taken offline earlier today as well, the second such attack on the site in the past week. And the website for French media conglomerate Vivendi, which currently owns Universal Music Group, remains offline as of 2 p.m. (PST). So, who’s next? A video allegedly representing Anonymous threatened to attack a litany of websites if Megaupload wasn’t put back online within three days’ time. That video (embedded below) was uploaded three days ago, we note, and it appears that whoever was behind it hasn’t followed through with the threats on that one. The list of potential targets included websites and services for the United Nations, Xbox Live, and U.S. Bank, as well as Twitter, Facebook, and YouTube.