Why go after end-users when you can ensnare them all in one fell swoop?

Russian Gang Hijacking PCs in Vast Scheme - The New York Times

As part of his investigation, Mr. Stewart charted the rate of computer infections at a state police agency and a large hotel chain. Both were victims of an outbreak that began after the gang obtained the password and login information of their network administrators. In both cases hundreds or thousands of computers were infected within minutes or hours.

Mr. Stewart would not name the organizations because of the continuing law enforcement investigation.

In these examples as well as a range of others, the gang infected a machine belonging to an administrator and then used Microsoft administrative tools to infect all the computers for which that person had responsibility, Mr. Stewart said.