A group called Control Your Info has hijacked a number of Facebook sites, aiming to call attention to privacy issues.
"We have seen too many examples where friends and relatives of ours have suffered from their lack of in-depth knowledge concerning their online presence," says the group on its website. "After some research we discovered this is a wide spread problem. People have even lost their jobs over Facebook content. We wanted to do something about this."
Using a quick Google search, the group found a number of sites that had been left without an administrator - and appointed itself. "We did not hack anything. Once we were administrators we owned the groups and could have changed any setting. We chose to change the picture, the name and the description of every group," it says.
The point is it making is that anybody could have done the same, but with rather more malign intent - linking a group with pedophilia, for example.
It says it isn't the only group to have acted in this way. "The search results also revealed many groups that already had been hijacked by various people. Their intentions remain unclear," it says.
Control Your Info says that, now it's got the attention it was after, it will change these settings back.
Facebook is trying to downplay the action, stressing that the sites had been abandoned. It says it will disable the affected groups.