The federal Securities and Exchange Commission has charged a Latvian man with participating in a pump-and-dump scheme that manipulated the value of more than 100 New York Stock Exchange and Nasdaq stocks. According to the complaint, filed Thursday, Igor Nagaicevs infiltrated the online brokerage accounts of victims to make "unauthorized purchases or sales" more than 150 times during a 14-month period. He then separately traded those securities to make more than $850,000 in ill-gotten profits, prosecutors said. The SEC filed a separate, cease-and-desist order against the firms that enabled him to make the trades, alleging they were not registered as brokers and allowed Nagaicevs to remain anonymous.