The CIA does not release any official numbers on the number of employees who work there, but estimates generally place it at somewhere around 15,000. Meanwhile a Pentagon report estimates the size of Iranian intelligence at around 30,000 or twice as large.
Iran’s intelligence service includes 30,000 people who are engaged in covert and clandestine activities that range from spying to stealing technology to terrorist bombings and assassination, according to a Pentagon report.
The report concluded that Iran’s Ministry of Intelligence and Security, known as MOIS, is “one of the largest and most dynamic intelligence agencies in the Middle East.”
The ministry actively supports Iran’s radical Islamic Revolutionary Guards Corps (IRGC) that has been involved in terrorist bombings from Argentina to Lebanon.
The size of an intelligence operation does not necessarily correlate with effectiveness, for example the Israeli Mossad clocks in at 1,200 people, but it does indicate the level of commitment and investment in intelligence operations.
And everyone is dwarfed by China which takes a "Put more men on the job" approach to everything and whose "human wave" espionage operations involve millions of people working for overlapping networks of intelligence agencies vacuuming up every piece of intelligence in sight.
Backing it all up is a Chinese intelligence bureaucracy back home that is huge, with nearly 100,000 people working just to keep track of the many Chinese overseas, and what they could or should, be trying to grab for the motherland. This is where many of the graduates of the National Intelligence College program will work.