Hackers broke into the website for Comcast overnight, replacing the cable and internet provider's web portal with a note.
Three apparent hacker groups -- Kryogenics, Defiant and EBK -- claimed responsibility, according to the note that appeared on the home page.
The hackers seized control of the Comcast.net domain name through DNS registrar Network Solutions and redirected it to servers under their control, according to published reports. The site was down for a few hours overnight but is operating normally, although some users are reporting email problems.
A Comcast spokesman said the company was working with law enforcement, reports said.
There has been no indication that any personal information was compromised. The company has 14.1 million subscribers for its online and other services.