Measures of secret information gathering are the way of gathering information which in a legally stipulated way temporarily restrict certain constitutional human rights and basic freedoms against citizens In accordance with Article 33 of the Security and Intelligence System Act, Croatian security and intelligence agencies may apply the following measures of secret information gathering:
 

1. Secret surveillance of the communication content,
2. Secret surveillance of the telecommunications traffic data,
3. Secret surveillance of the location of the user,
4. Secret surveillance of international telecommunications,
5. Postal censorship,
6. Secret surveillance and technical recording of the interior of facilities, closed spaces and objects,
7. Secret surveillance and monitoring, with recording of images and photos of persons in open and public spaces,
8. Secret surveillance and monitoring, with audio recording of the content of communication between persons in open and public spaces,
9. Secret purchase of documents and objects.