well, the US educated the designer...
from wikipedia
The Silkworm was developed at the Institute of Mechanics under Tsien Hsue-shen, a Chinese scientist who did his graduate studies at MIT and Caltech, before being deported by the United States in 1955 after being suspected of Communist ties. A book about this scientist's life was written by Iris Chang, entitled "Thread of the Silkworm."
The Silkworm gained fame in the 1980s when it was used by both sides in the Iran-Iraq War; both countries were supplied by China. More recently, the missile was used by Iraq in the 2003 Iraq War.
In March 1988, China agreed to stop supplying Iran with HY-2 missiles, though it is reported that supply continued into 1989. Iran has since developed the capability to manufacture these missiles itself.
In July 2006, it was reported that Hezbollah guerillas fired a "Silkworm missile" at an "Israeli battleship" off the shores of Lebanon. However this seems to be a typical case of media confusion over the term "Silkworm" as Israeli sources have said that the missile used was an Iranian-sourced C-802. At any rate, the damaged vessel was a Sa'ar 5 corvette, the most modern surface combatant in the Israeli Navy, and would have had little trouble dealing with a HY-series missile. Notably, Syria employed "Styx" missiles against Israeli warships in the 1973 Battle of Latakia with no success at all.
While it is not a particularly sophisticated missile when compared to others such as the Exocet, the Silkworm's unusually large warhead ensures that a single hit will inflict very serious damage.
Thanks, U didn't even think to check Wike.
I mean I didn't think to check.