In what appears to be the latest phase of a far-reaching federal crackdown on online piracy of music and movies, the Web addresses of a number of sites that facilitate illegal file-sharing were seized this week by Immigration and Customs Enforcement, a division of the Department of Homeland Security.

By Friday morning, visiting the addresses of a handful of sites that either hosted unauthorized copies of films and music or allowed users to search for them elsewhere on the Internet produced a notice that said, in part: “This domain name has been seized by ICE  Homeland Security Investigations, pursuant to a seizure warrant issued by a United States District Court.”

In taking over the sites’ domain names, or Web addresses, the government effectively redirected any visitors to its own takedown notice.

“ICE office of Homeland Security Investigations executed court-ordered seizure warrants against a number of domain names,” said Cori W. Bassett, a spokeswoman for ICE, in a statement. “As this is an ongoing investigation, there are no additional details available at this time.”