Protection Against Hackers

[Gemma]

I've jus had someone called SerSeri attempt to register on my site,I became suspicious wen I seen part of their email address so I checked out the link and then did a search on Google for SerSeri and true enough they belong to a site hacking team.

I also searched further and entered Serseri hacked and found that over the last few months many sites have been hacked by this person.

I've,obviously deleted the user and activated the 'registration by invite only' (which is part of a modification add-on),but I've never come across these hacker types before and would by grateful if someone could give me some pointers on how best to secure sites from attack.

Thank you in advance
Gemma