The yet-to-be-traced man had broken into the 42-year-old Moss sister's Facebook account and circulated her private pictures on the internet, reported AceShowbiz.
The leaked pictures include Moss' birthday party earlier this year and her on-and-off-again boyfriend Nikolai Von Bismarck.
"Kate isn't on social media but Lottie is quite open on all her platforms - although she has become far more guarded now.
"She realises she's a target for trolls who want information on her and her sister. None of the images were ever intended to be shared with the world so it's not very nice for them to have these personal moments pored over by some faceless hacker," a source said.