"Ratbert" sent out an offensive global message and attempted a DCC SEND exploit. He then killed off the network rights for every staff he could see and brought down quite a few of Freenode's servers.
At the time, users thought the whole thing was funny, but then started wondering how the hacker could have obtained staff passwords. Then they became concerned that Ratbert had managed to get their passwords too.
A spokesman for Freenode said it was entirely possible as the hacker had managed to gather NickServ passwords.
According to this bog, Freenode users think that this is unlikely.
If "Ratbert" had wanted to steal user passwords, he, she or it would most likely have done away with the servers quickly and as soon as he got his privileges, they reasoned.
Instead he spent most of his time knocking out staff members and generally behaving like a burke. µ