The Los Angeles U.S. attorney's office says 31-year-old Luis Mijangos was arrested Tuesday in Santa Ana.
FBI experts say he infected more than 100 computers used by about 230 people, including at least 44 juveniles.
The alleged scheme involved using peer-to-peer networks to infect computers, induce victims to download malware disguised as songs, and control those computers to spread malware through contact lists.
Mijangos allegedly searched computers for sexual or intimate images to blackmail victims into making videos for him. Prosecutors say he also was able to control some webcams to capture intimate scenes.