Depends on many things, in particular The exact brand of the system that you have. In general, the higher quality and more expensive security system that you have the less likely that it will be possible to control it from smartthings.
But then, if you have a more expensive security system, it is unlikely that you would be satisfied with a cloud-based controller anyway.
Some people have been doing some integration with Simplisafe. See the following topic
There are a few people who moved into houses where there were existing hardwired systems without an active Control Panel and achieved some minimal integration, so you can also search the forums for other specific brand names.