ANDROID is going from strength to strength. Around 600m of the nearly 2 billion smartphones ever sold use Google’s mobile operating system, estimates Horace Dediu, the boss of Asymco, a mobile-analysis firm. How odd, then, that nearly three-fifths of those that remain in active use, both old and new, rely on outdated versions of it. That is partly because old gizmos do not have enough oomph to run the latest iteration, called Android 4, and partly the outgrowth of Google’s choice to exercise only loose control over its operating system after each new version is released. The worrying consequence is that a vast number of phones do not receive software fixes, known as patches. Worse, many cannot be patched even if the owner wants to, says Rich Mogull, boss of Securiosis, an independent security-research firm. (..) As a result, tens of millions of phones run the version of the operating system with which they were shipped, perhaps with one or two minor tweaks. Even phones with the chips and memory to handle upgrades often do not receive them because of the support costs: handset-makers and carriers prefer to have consumers buy new phones than to provide technical support for old or outdated models.