The general staff of the ISI is composed of military officers of the armed forces as well as civilian officers from the FIA, FBR, Pakistan Customs, police and judiciary. They are recruited on deputations for 3 to 4 years and enhance the ISI's professional competence. Experienced army officers who perform well are given repeated extensions in their service. According to some experts, the ISI is the largest intelligence agency in the world in terms of total staff. While the total number has never been made public, experts estimate around 10,000 officers and staff, which does not include informants or assets.