The operators, Three UK and Three Italy, hope to win more customers by stopping the ads they consider excessive or irrelevant from crossing their networks. Other networks in the Three group could follow suit.
Mobile ads suck up bandwidth, which might seem a good thing for operators as they can charge for data by the megabyte. However, customers don't have limitless budgets, and so wasted bandwidth is more likely to reduce customer satisfaction than it is to increase usage.
The ads don't just clutter up Web pages: They also increase the size of app downloads and cause the apps to cache masses of ads for when they are used offline, causing inconvenience for those who can only afford phones with limited storage capacity.
Apple made a move against mobile advertising with a software update last year that allowed iPhone and iPad owners to download content filters from its app store. The company makes most of its revenue from sales of hardware, software and content, so has little to lose by blocking ads.
Samsung Electronics, which makes most of its money from device sales, attempted a similar move earlier this month, updating the browser in the version of Android it customizes for its phones to accept similar filters downloaded from the Google Play store.
Google, though, wouldn't play along, and promptly banned the content filters from its online store before relenting a few days later. It makes most of its revenue from sales of online ads, of which mobile advertising represents a substantial chunk.
Three UK and Three Italy are bypassing Google and its Play Store by blocking the ads in their networks, using software from Shine Technologies.
The operators don't want to completely eliminate mobile ads, which they say can be interesting and beneficial to their customers. Rather, they want to let the customer choose which ads they receive, letting them screen out ads that are excessive, intrusive, unwanted or irrelevant.
The relevance of advertising, of course, is typically improved by advertisers and advertising networks gathering information about customers' interests and online behavior -- in other words, through online tracking. The Three networks are aware of this, warning that some advertisers use mobile ads to extract and exploit data about customers without their knowledge or consent, and saying that their customers' privacy and security must be fully protected.
How they will do that remains to be seen: The companies said they will explain further in the coming months.
There will be technical challenges ahead. Much network traffic is now carried over HTTPS secure network connections as website operators and app developers see the benefits of encryption. To block ads, Shine and the operators will have to resort to techniques like blocking traffic based on its origin -- for example, all traffic from an ad network's servers -- or proxying the encrypted traffic using a fake certificate, so as to see inside the encrypted packets and pull the ads out.
Three UK and Three Italy also want advertisers to pay the data charges associated with the advertisements. They won't say yet whether ads paid for in this way will be considered more relevant or less excessive than ones for which they receive no payment.
German company Eyeo, the developer of the Adblock Plus extension for desktop browsers, has run into controversy because of its business model reliant on payments from advertisers. It says that it blocks ads based entirely on their intrusiveness, and that users may choose to view unintrusive ads using its software, regardless of whether it has received payment from the advertiser. Eyeo has now set up an independent board to determine which ads should be allowed through the filters employed by its software.
The networks in the Three group aren't the first to use Shine's ad-blocking software: Caribbean operator Digicel started using it last October.