Comcast is working an alternative to the so-called "six strikes" copyright alert system (CAS) that launched earlier this year in the US, according to a report on Variety. The system involves sending real-time warnings to illegal downloaders, along with a pop-up message indicating them where to buy or rent the content.

The thinking is that giving people accessible, affordable alternatives to illegal downloading will reduce infringement. Variety says the still-to-be-named scheme could be implemented alongside the current six strikes model, in which most major ISPs including Comcast already participate.

Under CAS, users are also warned that downloads are potentially illegal, and are pointed to legitimate sources; but generally this happens well after the event. The existing scheme also includes more aggressive 'mitigation measures' requiring users to confirm receipt of a third a fourth warning before they're able to continue browsing, and potentially facing throttled speeds or suspended accounts following the fifth and sixth warnings.

The country's largest cable operator is said to be in preliminary discussions with content providers and ISPs for a trial run of the technology. The pop-ups would reportedly direct to the video-on-demand library of any participating company or to a third-party such as Amazon, Hulu, Netflix, or iTunes. There's currently no indication that the system will cut off downloads identified as illegal if a user refuses refuses to opt for the legal route.

Further details are scarce at the moment so we're left with several unanswered questions for now. For one thing, the group behind CAS has yet to reveal any data since its implementation, so it's not clear how effective the technology is at identifying illegal downloads versus false positives. There's also very little information on how legal sources would be presented, and given Comcast's vast media holdings some are already concerned the system could prioritize some content sources over other potentially cheaper or more convenient ones.