Citadel Securities is seeking to join an insider trading lawsuit filed by Pennsylvania against Susquehanna International Group (SIG) and its former trader. Citadel aims to participate as a "victim" in the case, claiming losses from alleged insider trading activities involving U.S. stocks and options. The firm has requested permission from a New York court to intervene in order to protect its interests in future claims. The lawsuit accuses a former SIG employee of trading multiple stocks using non-public information for profit. The U.S. SEC is also investigating related allegations involving Susquehanna and certain U.S. stock options.