Earlier this month we noted how cable operator Mediacom has joined the growing number of ISPs that have begun using DNS redirection to deliver ads instead of the traditional page not found warning. Mediacom took things a step further and has apparently implemented deep packet inspection and DNS redirection advertising technology our users say is difficult to opt out of -- and persists even if you're using third party DNS services.

Now new complaints in our forums say Mediacom has started using Javascript to inject their own advertisements onto the top of websites -- including the normally stark Google main page. For illustration we've got screenshots of the Google and Apple websites after Mediacom is done with them.

Mediacom is literally intercepting website data and injecting their own code into websites in order to deliver ads where they weren't intended. The technology isn't new; if you recall Rogers was doing this back in 2007 in order to deliver ISP-specific messages using technology from Perftech. However, few ISPs have had the nerve to employ this technology for their own ads, given the inevitable backlash from consumers, ad networks, lawyers and potentially regulators.

Mediacom appears to have only started testing this "service" over the last week or so, and from looking at the Javascript files involved, it's the same Perftech technology employed by other ISPs. You can block such injections using Adblock, but you need to create a specific new AdBlock rule for the server the Javascript directs to. Users are given the ability to opt out of the ads, though as we've noted recently, Mediacom's opt out systems for their new advertising endeavors have not always worked. That's usually because some ISP executives are so thrilled by the new revenue potential new ad solutions offer, they stumble forward quickly ignoring technical (and sometimes legal and privacy) implications.

DPI tracking without informing your customers and broken opt out procedures are bad enough, but tinkering with websites and your customers' traffic for added revenue is something you'll find annoys paying customers -- who of course won't see the savings. There's some additional discussion about this in our Mediacom forum for those interested, including a message from a Mediacom representative saying it's being looked into as if it were some kind of bug (this is no bug). We've contacted Mediacom for comment and will share whatever information we get. We'd also be interested in seeing result links from any users willing to run a Netalyzr test.