Four toy companies have agreed to stop letting online marketers track children’s Internet habits.

Following a two-year investigation, New York Attorney General Eric Schneiderman concluded that Hasbro has , JumpStart Games, Mattel mat , and Viacom viab violated the Children’s Online Privacy Protection Act (COPPA).

The probe, dubbed “Operation Child Tracker,” revealed third-party vendors used cookies and IP addresses to track kids under 13-years-old, giving them access to some of their personal information without first receiving their parents’ approval. Sites that improperly tracked children’s online activity included Nickelodeon, American Girl, Neopets, and My Little Pony, among others.

“Federal law demands that children are off-limits to the prying eyes of advertisers,” Schneiderman said.

The companies will be paying a combined $835,000 fine, according to a press release—and each agreed to reform its systems to protect kids from invasive tracking. The four companies have also agreed to take new measures to protect kids from being tracked by online marketers. This includes scans to monitor for third-party trackers, thoroughly vetting third-party’s data collection practices, and informing third-parties that a website complies with COPPA.

 

We have cooperated fully with the New York Attorney General’s office on the investigation and welcomed the opportunity to bolster our privacy practices in connection with today’s settlement,” a Hasbro spokesperson told Fortune. “Moving forward, we will be more closely vetting and monitoring companies that work on our behalf.”

Mattel shared a similar sentiment.

“Mattel takes online privacy and security very seriously, and we care very much about the privacy of those who use our websites,” a company spokesperson told Fortune. “Anytime we become aware of a question about whether a Mattel-operated website is in full compliance with the Children’s Online Privacy Protection Act (“COPPA”) or other laws, we take prompt action to investigate and, if necessary, remedy the situation and look for additional controls to avoid a reoccurrence of the issue.”

Viacom also said that it “takes very seriously its longstanding commitment to protecting children’s privacy, and we work hard in today’s fast-changing digital landscape to insure our COPPA compliance.”

JumpStart Games could not immediately be reached for comment.