This guide is to help people root their Galaxy S4 Active devices. Model SGH-i537 on AT&T.
proceed at your own risk :
1. First go to Settings and click the "More" tab. Then go into security and check "Unknown Sources."
2. Visit http://geohot.com/activeroot from your device and click the lampda picture to download the apk file.
3. Run the apk. It should give you a message telling you that you have root. Worked almost instantly for me.
4. Visit the Play Store and download SuperSU. (NOTE: You MUST download and use SuperSU to manage superuser permissions, nothing else. Only SuperSU currently can circumvent Samsung's "root blocker" in the kernel.)
5. Open the Super SU app and update binaries.
Kill AT&T's OTA updater before it kills you!
Use a root enabled file explorer (Like Root Explorer) and navigate to: /system/app/
Rename or delete wssyncmldm.apk
If you want to get rid of AT&T's nannying nagging message about root access delete or rename KNOXAgent.apk
Install App Quarantine, go into settings and uncheck Hide system apps and disable AT&T Updater
UNROOT and RETURN TO STOCK:
File Name: Oneclick_I537UCUAMF1.7z