Read all about it:
http://www.globalsecurity.org/military/world/iran/ships.htm
"On 04 August 1993, Iran took delivery of a second Russian Kilo-class diesel submarine, and the third arrived 18 January 1996. Russia went ahead with the first two deliveries despite vigorous US protests. In response to Administration pressure and US sanctions legislation, Russia formally pledged in June 1995 not to enter any new arms contracts with Iran, although prior arms contracts could be implemented."
Those subs may be quiet, but they are now ten plus years old and would be operating in a relatively shallow sea which I guarantee has more than a few listening devices. I doubt they ever dock outside well known Iranian slips, and I doubt they world cruise because of logistics. I bet their communications are compromised. So I suspect we know exactly where they are.