fishing expedition
noun /ˈfɪʃɪŋ ekspədɪʃn/
/ˈfɪʃɪŋ ekspədɪʃn/
- a search or investigation carried out in order to discover any information about a person, organization, etc. that might be used to harm them
- There's a danger that the system could be used to conduct fishing expeditions rather than targeted surveillance.