Grima Wormtongue, King Theoden's adviser, was Saruman's informer
at Edoras, the court of Rohan. In the Shire and surrounding lands,
Saruman had other informers, such as the Southerner the hobbits saw
at Bree, something of a half-orc breed. Also Bill Ferny was in
league with Saruman. These ruffians are how Saruman was able to
obtain his pipe-weed.