Shin Bet identified the brothers as Mahmoud Abu Qedar, 23, and Sameh Abu Qedar, 20, and said the Jews, one a soldier, provided them with weapons. The Jews were not identified. The arrests were made in December and January.
The two brothers admitted to, among other things, contacting terror operatives in the Gaza Strip and abroad, purchasing explosives, assembling rockets, planning a suicide bomb attack at a bus station in Beersheba and an attack on the city's train station, the agency said.
Mahmoud Abu Qedar said he purchased ammunition from the Israeli soldier in exchange for drugs, investigators said.
"This is a grave incident in which Israeli civilians, residents of the Negev, planned terror attacks against Israeli civilians and Israeli security forces," Shin Bet said.