[AT&T Samsung Galaxy S 5] cstayton:
Guide: Howto enable Native AT&T / Tmobile WiFi Hotspot​

Locate stock/unmoddified TetheringProvision.apk

This apk is located in /system/app folder from almost any Stock Samsung ROM

Or pull from your device.

connect your device to your PC

Make sure you have the appropriate USB drivers installed

make sure Android SDK Tools are installed

cd to the platform-tools folder in the SDK location

start a command prompt in the Platform-Tools folder

adb pull /system/app/TetheringProvision.apk

Using available tools to decompile and recompile the apk

I recommend either Virtuous Ten Studio or APK-Multi-Tool for this task as

either provide an easy to use interface for working with apk edits.

I'm not placing download links here for either just do a google search and

you will easily find either one.

Decompile the TetheringProvision.apk

Once you have the apk decompiled browse to the folder containing

all of the decompiled code (You will need to be in the smali folder).

locate and edit "TetheringProvisionActivity$TetheringPlanCheckTask.smali"

(com/sec/tetheringprovision)

For AT&T WiFi Hotspot

search for "entitlement.mobile.att.net" and replace with "stacra.byethost7.com"

search for all instances of "http://entitlement.mobile.att.net/mhs1" and replace with "http://stacra.byethost7.com/tether/"

search for all instances of "http://entitlement.mobile.att.net/teth" and replace with "http://stacra.byethost7.com/tether/"

For Tmobile WiFi Hotspot

search for all instances of "http://selfhelp.geo.t-mobile.com/myaccountservice/selfhelp/hastetheringoption"

and replace with "http://stacra.byethost7.com/tether/"

See code snippet below for example (not complete code)

The lines you will be looking for are highlighted in blue.

.prologue
.line 1116
iput-object p1, p0, Lcom/sec/tetheringprovision/TetheringProvisionActivity$TetheringPlanCheckTask;->this$0:Lcom/sec/tetheringprovision/TetheringProvisionActivity;

invoke-direct {p0}, Landroid/os/AsyncTask;-><init>()V

.line 1117
const-string v0, [COLOR="Blue"]"http://selfhelp.geo.t-mobile.com/myaccountservice/selfhelp/hastetheringoption"[/COLOR]

iput-object v0, p0, Lcom/sec/tetheringprovision/TetheringProvisionActivity$TetheringPlanCheckTask;->TMobileTetheringPlanCheckURL:Ljava/lang/String;

.line 1118
const-string v0,[COLOR="Blue"] "http://entitlement.mobile.att.net/teth"[/COLOR]

iput-object v0, p0, Lcom/sec/tetheringprovision/TetheringProvisionActivity$TetheringPlanCheckTask;->ATTTetheringPlanCheckURL:Ljava/lang/String;

.line 1119
const-string v0,[COLOR="Blue"] "http://entitlement.mobile.att.net/mhs1"[/COLOR]

iput-object v0, p0, Lcom/sec/tetheringprovision/TetheringProvisionActivity$TetheringPlanCheckTask;->ATTMHSPlanCheckURL:Ljava
/lang/String;
...
...
...

Once you have located and replaced all the required lines in the smali save the file and recompile your apk following the instructions provided by whatever method you choose to work with

DO NOT SIGN THE APK LEAVE THE EXISTING SIGNATURE IN PLACE

Push the apk back to your device and reboot, test to verify working Hotspot.

Thanks

Thanks to [MENTION=426561]scrosler[/MENTION] over at the LG forums for the original code of this patch

it has been changed and revised a few times since the original port by me over

in the HTC Forums.