Executive Producer Abdul Karim of Sphere's Origin (Saat Phere, Grihasthi)
"Normally we hire our own guards on the sets. They work in 12-hour shifts and know their job completely. They will never allow anyone to enter the sets. Our unit also tries to be alert. When we shoot outside the studio, security is always present."
All in all, actors and production houses take lots of precautions and try to avoid robberies, but still such kind of incidents do take place as it is very difficult for them to keep an eye on such a vast location and on every outsider. Some studios have many entrances and even unprotected places from where anyone could easily peep inside the set.
Guys,
I didnt attach the whole article, but there are others who talk about their safety as well. You can read it here:
http://www.indya.com/news/newsDetails.aspx?xfile=2008/April/ News_20080401_9
Guess Sphere Origins production house is safe. That's good for our castđ