The practice of curing and smoking meat is one of the oldest forms of food preservation. Treating cuts of meat with a salt solution or packing them in dry salt inhibits most spoilage bacterial growth by reducing the amount of water available for bacteria to grow.
Smoking meat adds an appealing smoke flavor, but it also uses three mechanisms to preserve the meat. Heat will kill bacteria, depending on the time and temperature used. Chemical compounds from the smoke have an antimicrobial effect. And finally, the outer surface of the meat dries, which reduces moisture available for bacteria to grow.
For a review on curing and smoking meats, see the extensive information in the University of Georgia review of Smoking and Curing.