1 Check your Host file by going to gs.apple.com in you computers browser.
2 if you see a TSS or Cydia page you need to clean your host file until you see this page.
3 make sure your iTunes is up to date.
4 Enter DFU Mode
Do not use any jailbreak tools to enter DFU Mode ( that would be Pwned DFU ), all you should have open is iTunes and follow these steps.
EASY DFU: Plug device into computer via USB. Don't look at the device, concentrate on the counting. Hold home+power for 10 seconds, then release power but keep holding home for 12 more seconds. Screen should be black
5 open iTunes and just hit " restore iPhone "
Do NOT try and restore any 6.x IPSW's just hit " Restore iPhone " and let iTunes download the newest IPSW ( 7.0.2 ) ATM or it will fail..
You may also refer to this:
If you try all of those and still can't get your iPhone recovered, I suggest you to use Myjad iTunes Backup Extractor first to restore important information to your PC local .
Check out from here: