It is believed 1,000 survivors have had “highly sensitive and personal” information stolen.
The data of hundreds of sexual abuse victims has been stolen in a ransomware attack.
The attack targeted a company that manages data for around 140 charities and non-profit organisations in Ireland, Northern Ireland and the UK, was targeted by cyber criminals last month.
It is believed 1,000 survivors have had “highly sensitive and personal” information stolen. When alleged perpetrators and others are included, the number of people affected is believed to be around 2,000.
It is now believed fraudsters may attempt to contact the organisations and people whose data they have stolen in an attempt to extort money from them.
A spokesperson for Derry-based Evide said that as soon as it became aware that its systems had been accessed, it contacted the police and engaged cyber security specialists to help it contain the issue and support recovery efforts.
None of the material stolen, which is described as "highly sensitive and personal information", has so far been published on the darknet or other online forums.
The four organisations are located in Dublin and the south of the country and include One in Four, which helps adults who have experienced childhood sexual abuse.

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