TRENTON, N.J. - Internet use of more than 4,000 high-risk sex offenders in New Jersey could be sharply curtailed under a new law signed Thursday.

State parole officers will soon be allowed to conduct unannounced computer searches of high-risk sex offenders under their supervision, and in some cases, install software that monitors their online activity.

And starting in late February, sex offenders who used the Internet to commit their crimes will no longer be permitted to go online unless it's related to their job or if they are looking for a new one. Judges will be required to impose that restriction at sentencing.

Violators could face up to 18 months in jail, and those using the Internet in an attempt to commit another sex crime would face at least five years in prison.

Officials cautioned that the new law is not a panacea, since libraries, Internet cafes and cellphones with online services still give sex offenders plenty of opportunities to use the Internet.

But acting Gov. Richard J. Codey, who signed the new law Thursday, said it will maintain New Jersey's role as a national leader in the protection of children against sexual predators.

"Every day we hear another horror story about some unsavory character using the Internet to prey on our children," Codey said during a bill-signing ceremony at New Jersey State Police headquarters in West Trenton. Codey is filling in for Gov. Jon Corzine, who is vacationing out of the country.

The new measure supplements New Jersey's Megan's Law restrictions, which require law enforcement officials to notify residents when a high-risk sex offender moves into a neighborhood. The law, enacted in 1994, is named after Megan Kanka, a 7-year-old girl who was raped and murdered by a twice-convicted sex offender who lived on her street in Hamilton, a suburb of Trenton.

Only two other states, Florida and Nevada, already restrict the Internet use of convicted sex offenders.

"This is landmark legislation," said state Assemblywoman Linda Greenstein, a Democrat whose district includes Hamilton.

Critics of the new law questioned whether the Internet restrictions are too harsh, given they will keep sex offenders from going online for support or education. They said it made more sense to let a panel that will soon meet to evaluate Megan's Law to consider Internet restrictions.

The new law also comes as the state is ramping up other efforts to prevent sexual predators from using the often anonymous world of cyberspace to find new victims.

Earlier this year, the operators of the social-networking site MySpace determined that more than 7,000 known sex offenders, including many from New Jersey, created profiles that were used to communicate with others.

The state, through Attorney General Anne Milgram, issued subpoenas to MySpace and other social networking sites to track the profiles of convicted sex offenders. Milgram's office also asked the sites to voluntarily post a "Report Abuse!" icon so users could help catch online predators.

Also, 41 people were arrested in a statewide sting in October that targeted the swapping of child pornography images using the Internet.

In November, the state Parole Board voted to prohibit sex offenders from using networking sites to socialize.

Codey introduced the legislation in 2006 and it passed unanimously in both the Assembly and Senate earlier this month.

New Jersey State Police Lt. Anthony Ritter said the new law will help law enforcement better control what he called "the Wild West on the Internet."

(c) 2007, North Jersey Media Group Inc. Distributed by McClatchy-Tribune Information Services.