Social networking site MySpace and its parent company News Corp are being sued by four families after their teenaged daughters were sexually assaulted by adults using the website. 

The four separate cases, filed by families in Texas, Pennsylvania, New York and South Carolina, are seeking millions of dollars in damages.

The cases include a 14 year-old New York girl who was raped by two men; a 15 year-old girl from Texas who was drugged and assaulted; and a 15 year-old Pennsylvania girl and two sisters aged 14 and 15 from South Carolina.

MySpace introduced its Zephyr monitoring software yesterday, which lets parents see what age, name and location their children are displaying online at the site.

However, the site warns the children that their information has been shared and does not allow the parents to read their child's email.

MySpace appointed a security chief in 2006 and has partnered with police forces to try to make the site safer for teens. 

Jason Itkin, a lawyer acting for the New York girl's family, said that, despite the efforts, MySpace had waited too long to bring in meaningful security measures. 

In a separate incident yesterday, two guards at a juvenile detention centre were sacked for trying to chat to teenagers using MySpace.

John Stone and Anthony Berrios from the Medina Juvenile Detention Center set up an account using the name '2wildandcrazyguys' in a bid to target high school girls in the area who had been in juvenile detention.

The alarm was raised by a girl who informed her teacher, and both men were fired following an internal investigation.