The perils of making friends via social networking websites have never been clearer, but warning signs have abound after cases such as murder and theft have been linked to some friends found through Facebook and other social networks.

Aussie teens are given a warning after a Sydney-based man confessed to the murder of an 18-year-old he met through Facebook.

Christopher James Dannevig, 21, of Leumeah, pleaded guilty to murdering 18-year-old Nona Belomesoff in May 2010 and is now awaiting sentencing from the NSW Supreme Court.

Reports from the Herald Sun said Dannevig was committed to the NSW Supreme Court for sentencing on October 7, after the gulity plea was entered at Campbelltown Local Court on Wednesday.

Belomesoff from Cecil Hills vanished after telling her family she was going to meet two males she befriended on Facebook, who offered her work with the Wildlife Information and Rescue Education Service (WIRES). Days later her body was found in a bushland near Warminda Oval at Campbelltown.

Police believed the second man does not exist. Dannevig was accused of setting up a fake identity on Facebook before luring her to a meeting with the promise of work.