The ONLY people that create iPhone jailbreaks are part of the iPhone-Dev team or Chronic-Dev team. When an untethered jailbreak is created you will hear about it from their websites/twitter before it's even released. If that doesn't happen and someone claims that an untethered jailbreak is released, they are lying. Simple as that.
In the off chance that some unknown person actually did release a working untethered jailbreak, the respected hackers would still post about it on their websites or their twitter. The moral of the story is unless you hear the news from someone reputable: musclenerd, i0n1c, ih8sn0w, comex, chpwn, etc. then it's a lie.