[Acer Iconia A500] timmyDean:
No, the backdoor idea is exactly what it says it is. It is a way to get back into a system after they change security when you install an OTA.

To understand what happens during an OTA, is that it is only doing an update. Meaning they update the /system folder and replace (sometimes only updating) everything in /system/app. They may also update the boot and other areas of the device such as / (root folder). However, they don't wipe it totally clean (or most don't). That's why when you get an OTA, for example, you don't have to type in all your contacts again etc. Or reload all your applications you installed from the Marketplace.

During this update process, the last thing they do is reset all the permissions recursively in the /system folder to their default and in doing so remove the 'sticky bit' that gives you root. Most people consider rooting as loading busybox, su, and a Superuser.apk. If you look after the update, you will see su and busybox (normally) are still loaded, just the permissions have the 'stick bit' removed. The Superuser.apk will be missing because they often replace the /system/app folder.

So, what happens in the Android market, is OEM's fix things and push updates. Fix to WiFi, GPS, NetFlex etc and push an update. After the update, the user finds root (#) not working. So they use the exploit that gave them root and re-root the device. Unfortunately, as fast as developers are finding exploits, OEM's are patching them.

In the ACER 3.0.1 there are several exploits to gain root(#) access that have been removed in 3.2.1. Therefore, if you do the OTA's you loose root and then you try to use your exploit to gain root, you get a surprise. The OEM has patched that hole.

So, what you do is create a backdoor that allows you to gain root access outside the normal /system folder and 'sticky bit'. Therefore, when an update occurs, you can get back in as root.

Now, for the ACER. If you have an a500 ACER 3.0.1 Stock, then you can gain root by simply using GingerBreak (Iconiaroot for example). However, if you take OTA's you will loose root and GingerBreak will no longer work. So, since you have root, you create a backdoor, now when you apply the OTA's and it removes the GingerBreak exploit; all you have to do is use your backdoor to get back in as root and set back up bussybox, su, and Superuser.apk.

== Now the current state of the a500 ACER ===

Earlier versions of the a500 had exploits that we used to gain root. These exploits were all removed in 3.2x. What people found out, was that if they had root they lost it once they upgraded. Or, if they bought it new, and it had 3.2x there was no way to root it.

Therefore, the only solution, at first was to rollback your device to an earlier version that allowed rooting and to stay there or use CWM to apply a modified update of 3.2x with root. Using CWM is a major tool used to replace ROM's or replace with custom ROM's.

However, now the catch 22. In 3.2x, ACER locked the bootloader and by doing so, it prevents you from installing CWM. Because you cannot install CWM, you cannot install custom ROM's or custom updates.

3.2x closed all known exploits, but ACER left the ability to rollback to an earlier version. If they would not have done that, then we'd be stuck (screwed). So, you basically have to rollback to a version you could exploit and then stay there, or load a custom ROM, or install CWM and install a modified update.zip to get you to 3.2x.

If you don't want to stay there and want to apply OTA's then you have to build a backdoor so you can get back in after the OTA's remove your normal root(#).

Hope this helps,

TD