The .ASEC extension belongs to the popular mobile OS file medium of Android. The file type ASEC refers to Android Secure encrypted packages. Introduced with the Froyo (build version 2.2), the ASEC file have become one of the standard formats for encrypting package data on the android platform.

Typically, Asec files provide security on the SD card and other such external storage mediums thus enabling authentication for the android data. It is helpful for preventing unauthorized deletion and modification of android data files. The file structure is designed in such a way that it encrypts files only of the applications on the external storage and no such functionality is available for phone memory. Hence ASEC files automatically decrypt to APK packages upon moving the apps to phone memory.