The "USB PC Connection" in the "Settings" is no longer available. So, now, how do I check/change my USB settings on Android 4.3 on my S3?
Here's how.
1. Ensure that you have downloaded and installed the USB driver on your PC for your phone from:
http://www.samsung.com/us/support/downloads (select the model of the phone)
2. Enable Developer Options:
• Settings > More > About device
• Scroll down to "BUILD NUMBER"
• Tap it a couple of times (about 5 times) - an alerts tells you how many more times to tap
• "Developer options" would now have appeared (Settings > More > Developer options)
• Under "Developer options", tick the check box for "USB debugging"
3. To change the Qualcomm Modem settings, dial *#0808# for Android 4.3 (*#7284# on Android 4.2)
4. You will see the following screen:
5. For me, "MTP + ADB" worked. (MTP = Media Transfer Protocol)
6. Click "OK". If your PC does not detect the phone, reboot the phone.
You should not be able to access your phone via a USB connection on your phone running Android 4.3.