Over the weekend, unofficial Snapchat apps for Windows Phone, including the popular 6snap, were unceremoniously yanked from the Windows Phone Store, preventing any future downloads and updates to those apps.

Snapchat has not developed an official app for Windows Phone users, and it does not have any official API for third-party applications to use. Over the last few weeks, the company has been contacting users of third-party applications to warn them that their accounts may get locked out. This crackdown came in the wake of a large leak of Snapchat images that were stolen from the third-party service SnapSaved, an app some Snapchat users were currently using to save the pictures they were sent.

These third-party applications worked by reverse engineering Snapchat's internal APIs, and they have filled the gap on platforms that Snapchat does not support. 6snap developer Rudy Huyn has said that Snapchat still has no plans to develop an unofficial Windows Phone client, leaving users of the minority platform in the lurch.

Snapchat itself came under fire after the SnapSaved incident. The company was perceived as not doing enough to keep people's pictures "safe."

The problem for Snapchat is that its entire product is built around the DRM proposition: the Snapchat apps themselves through necessity contain all the information needed (both in terms of API calls and any relevant encryption keys) to both retrieve Snapchat pictures and show them on-screen. The automatic deletion of those pictures is not enforced by any policy or intrinsic feature of the pictures; it's simply something that the Snapchat app chooses to do.

For Snapchat users, this deletion feature is the service's raison d'être. SnapSaved made it abundantly clear that there's nothing Snapchat can actually do to enforce this feature, however, and that's not good for Snapchat.

Third-party developers who wish to access Snapchat thus need only to run the official Snapchat app on iOS or Android and monitor what those apps do. Snapchat has no way of keeping secrets from end users.

And Snapchat's security is only being further scrutinized due to its planned Snapcash feature that will allow people to send money to one another over the service.

As such, a crackdown is unavoidable. While Snapchat can, of course, be certain that its own apps will honor the time-limiting feature of the platform, it has no way of forcing third-party applications to do so. And while many third-party applications do honor the spirit of Snapchat, some, such as the problematic SnapSaved, do not. Sometimes their refusal to honor the spirit of Snapchat can be the entire point—defeating the automatic deletion feature of the official Snapchat clients was SnapSaved's entire purpose.

6snap isn't the only Snapchat app to have fallen foul of Snapchat's opposition to third-party applications. Last year, the Windows Phone app SwapChat was published and then pulled, presumably because of complaints from Snapchat.

Nonetheless, third-party Snapchat apps seem to still be available from Google Play Store and on the iPhone App Store. At the time of writing, the second hit for a search for Snapchat on the App Store is "SaveSnap - Save SnapChat Pictures." The fifth hit on the Play Store is "SaveMySnaps."

Users of such apps may still have their accounts locked by Snapchat. Third-party developers aren't yet clear on just how Snapchat is identifying their activity, though there is some speculation that those apps are using Snapchat's APIs a different amount than the official app does.