"Surveillance activities" refer to the actions or methods used to closely observe and monitor people, places, or activities for the purpose of gathering information or ensuring security. Full definition
If you were (and I'm betting you weren't) involved in surveillance activities you aren't allowed to discuss them irrespective of whether your stories are accurate or not. (religion.blogs.cnn.com)
Enter and retrieve information from computer database and hard copy files in order to utilize such information in surveillance activities. (jobhero.com)
WASHINGTON, April 18 - Four U.S. senators on Wednesday urged the U.S. Homeland Security Department to disclose additional information about unusual cellular surveillance activity that has been detected around the nation's capital. (cnbc.com)