"Undercover investigation" refers to a secret operation where someone gathers information or conducts research secretly by pretending to be someone else or by blending in with a particular group. Full definition
Animal nonprofits actively pursue this goal by conducting undercover investigations of factory farms in the hopes that media coverage of their findings will convince readers and viewers to eat fewer animal products. (animalcharityevaluators.org)
That makes it much more difficult to document in undercover investigations. (chicagonow.com)
Although it's up for debate whether the law covers commercial dog - breeding operations, it has been a deterrent to those who would pursue undercover investigations. (chicagonow.com)