They reversed enginered them from missiles bought from Russia and China, Iran is a missile maunfacturing plant in itself.
Both the Yakhonts and the Sunburn missiles are designed to defeat the Aegis radar defense currently used on U.S. Navy ships by using stealth technology and low ground hugging flying maneuvers. In their final approaches these missiles take evasive maneuvers to defeat anti-ship missile defenses. The best defense the Navy has against Sunburn and Yakhonts cruise missiles has been the Sea-RAM (Rolling Actionframe Missile system) anti-ship missile defense system which is a modified form of the Phalanx 20 mm cannon gun . The Sea-RAM has been tested with a 95% success rate against the 'Vandal' supersonic missile capable of Mach 2.5 speeds but does not have the radar evading and final flight maneuvers of Russian anti-ship missiles.
Although Van Riper mainly used Silkworms and scuds, using asymetrical warfare it shows how new technology since then would make it that much harder.
Some links on the destruction of the fifth fleet by Van Riper...
www.guardian.co.uk/g2/story/0,3604,786992,00.html
www.wikipedia.org/wiki/Millennium_Challenge_2002
www.badattitudes.com/ArmyTime.html
http://www.strategypage.com/dls/articles2002/20020911.asp
Just think, if Van Riper could accomplish what he did with Silkworms and scuds, imagine what could happen if the US Navy, sitting in the Gulf like so many ducks, should face a massed-attack of supersonic Yakhonts missiles, a weapon that may well be unstoppable.