The group allows Facebook users to join and post photos and information about the goods they want to sell locally. They can connect directly with buyers, and until a few days ago anyone who was a member could invite others to join.
Ms Hudson and her partner, Campbell Tobin, took over administration of the group four days ago and spent six and half hours at the weekend working their way through all the members, identifying the trolls and removing them.
They found hundreds of members, mainly from overseas, who they believed were actually fake profiles and not real people, although variations on the names Ranjit and Jocko popped up regularly. The same names were involved in scamming incidents on a similar trading site in New Plymouth this year.
Ms Hudson said she passed several names on to Facebook and noted related profiles were since removed.
The fake members and offensive posts were removed from the Dunedin group and the offensive posting had ceased, so she believed they had correctly identified the culprits. Any new members to the site now had to be approved by the administrators.
Ms Hudson said the thought of someone using her children's photos was "horribly upsetting".
One of the victims of the trolls, Dunedin man Rodney Feron, said he was now making sure his privacy settings were correct. He wanted people to be aware that trolls could be working on any internet group.
NetsafeNZ executive director Martin Cocker said attempts at blackmail by internet trolls were becoming increasingly common.
People have been convicted for trolling - in Australia a man was sentenced last year to three years' jail after he posted pornographic images on the tribute pages for two slain Brisbane children. Another man in England was jailed for comments made on Twitter about Fabrice Muamba, a footballer who suffered a heart attack during a Premier League game.
Mr Feron said he had contacted the police about this incident but was told there was little they could do with such threats from overseas.
- Otago Daily Times
