The article said the virus was released outside of any government facility, and by now has probably infected millions of PCs in that part of the world. It won't do anything except reproduce itself, unless it finds itself inside the weapons private network. Then it gets busy.
The good guys just had to wait for someone to bring the infection inside. They probably "lost" a laptop or USB drive on a bus, and waited for someone to "find" it. Maybe they enhanced the bait with some files like "Best of Goats 2010 centerfolds, and 2011 calendar". Multiple infection sites would speed things up even more.
It won’t do anything except reproduce itself, unless it finds itself inside the weapons private network. Then it gets busy.
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According to the article it will only “get busy” if it finds Siemens controllers working P-1 centifuges in a certain configuation, else it remains dormant. It is very specific, not gerneric, in its targeting.