Bothan SpyNet is a technology that can be researched at the Fortress in Tech Level 4. It costs 100 Nova per enemy worker, and lets the player see everything that the enemy can see. In Terminate the Commander games, it is replaced by the Commander Locate technology, which temporarily reveals the position of all enemy Commanders.
This is an extremely powerful technology, but the cost will be too steep in most games. It is most useful for hunting down the last few survivors after taking down the enemy base, when they will have too few Workers for the price to be a problem.
"The SpyNet grants you the ability to see what your opponent sees."