Nebraska Gov. Dave Heineman has signed a bill to prevent registered sex offenders from using social-networking sites such as MySpace or Facebook.

The bill also expands the crime of online enticement to include communications through electronic devices other than computers, such as cell phones.

Attorney General Jon Bruning cited a study that found that 76 percent of offenders convicted of Internet-related crimes against children also admitted to sexually assaulting children.

The bill would create an exception for teens who knowingly send nude pictures of themselves to another minor and for those under age 19 who receive a picture from a person who is at least 15 but don't forward that picture to others.