Felix Sanz, the head of Spain's National Intelligence Agency (CNI), unveiled plans to boost the service by hiring another 500 personnel by 2020 to combat the "growing jihadist threat".
Speaking at a security conference on Thursday, the CNI chief was optimistic. "We're winning the fight" against jihadist fanaticism, he said according to a report in El Pais, citing recent successes against Islamic State on the ground in Iraq and Syria.
But he admitted that defeating Isis could take years.
New recruits to the CNI are being sought in the fields of mathematics, telecommunications and computers; expertise needed to thwart a new breed of terrorism that increasingly uses new technology and social media.
During the seminar Francisco Martínez Vázquez, Spain's secretary of state for security revealed that an estimated 170 Spanish residents have left to join the ranks of Isis.
Of those around 20-25 have returned to Spain where they are either in custody or on a watch-list. The figure is significantly lower than that in other European countries such as France or the UK.