“Security experts warn that Islamic militants in the Caucasus, who have threatened to derail the Winter Games that run from Feb. 7-23, could achieve their goal by choosing soft targets away from the Olympic sites or even outside Sochi. Some have raised the possibility that jihadists could have infiltrated Sochi long before security was tightened and have noted the vulnerability of the city’s transport systems.”
Source: Suicide bombers called biggest Sochi Olympics risk – Houston Chronicle