"During covert operations or police investigations agents may routinely claim to be of political views or a part of an organization in order to gain the confidence of the people they wish to surveil. Sometimes this goes further with the agents participating in acts on behalf of the organizations they infiltrate or falsely represent as was the case during the Operations like Gladio and Chaos. Often the end goal is not just to gain information about the organization but to discredit them in the eyes of the public. However, these kinds of actions are more similar to false flag operations than typical undercover operations. In other examples, operatives may act in a manner they deem positive to assist an organization to which they cannot have overt ties." - https://en.wikipedia.org/wiki/Shill