To learn something about this string theory it is natural to start by focusing upon any degrees of freedom that are manifestly string-like and, in linearly confining theories such as SU(N) gauge theories in D=2+1 and D=3+1, these are long confining flux tubes. One can ask what effective string theory describes their dynamics. Recently there has been substantial analytic progress (Luscher-Weisz, Drummond, Aharony, ...) towards answering this (old) question which, roughly speaking, tells us that the dynamics governing very long flux tubes is, to a certain approximation in powers of 1/l, that of a Nambu-Goto free bosonic string theory.
At the same time numerical lattice calculations of the low-lying excitations of closed flux tubes in D=2+1 and D=3+1 have shown that (nearly) all the calculated energies are remarkably close to those of the free bosonic string theory even when the flux tube length l is not much greater than its width so that an expansion in powers of 1/l no longer converges.
This is an area in which interesting progress is
being simultaneously made from various analytic and numerical directions.
For an overview see the talks at the recent Workshop: