A custom recovery is an alternative recovery environment for Android-style devices. Unlike the stock recovery built by the vendor, it is designed for advanced maintenance tasks such as factory resets, image flashing, partition backup, and sideloading updates. On locked consumer devices, reaching a custom recovery often requires an unlocked bootloader, because the recovery partition is part of the device’s trusted boot chain.
In cyber security, custom recovery matters because it can change the device’s trust model. A legitimate administrator may use it for repair, forensics, or controlled firmware installation, but an attacker who obtains unlock capability can use the same path to install modified system images, bypass some vendor controls, or make post-compromise changes that survive normal reboots. For defenders, an unexpected custom recovery or an unlocked bootloader is a strong signal that the device may no longer be in its original integrity state.