Just wondering - how can they link a WoW account with a Battle.net account without knowing the WoW accounts password and security questions to authorise it - presumably by sending an "ok to link account" email to the WoW email account?
That's exactly what happens, but if a hacker gets your username and password, the first thing that they will change on your account is the email address. This then allows them to have complete control over it because all authorisation emails are sent to the new address.
From the way many people have posted in this thread it's almost as if all they need is the WoW account username/password and they're good to go. Surely at some point the WoW account should be kicking out an e-mail warning of changes to e-mail/account status.
As above, this is all they need to get into your account and take ownership of it.
It sounds like whoever is doing the hacking is spamming mergers on the battle.net site with random account names.
They are definitely not spamming at all. They have the username and password for all accounts that they want to merge. You can't merge an account without this information, so that means that there is a keylogger, trojan or malware on the PC that the account information was stolen from. Most of the time they capture the username and password when you log into WoW. They then use this to go through the merge process into a new Battle.net account, and finally they clear out all your stuff on your characters. There is no uncertainty involved, they do this all with the information that is required.
It's a sad day when you have to start buying bank style authentication devices to protect a game account from fraud, sounds like Blizzard should have forced password changes every few months on accounts with more strict password strengths.
I agree but Blizzard implemented their Authenticator system when they realised that a lot of accounts were being targetted, and that a lot of people are lazy with their internet security. As mentioned above by Mercutio, and by me earlier, it is very simple to maintain a good security routine. I don't understand why people don't seem to bother, especially when they have so much to lose. You can get very decent security packages for absolutely nothing if you go to the right places. I'll list them again:
AVG Free Edition
Spybot S&D
Comodo Personal Firewall
Mozilla Firefox
NoScript Addon for Firefox
These are what I use at home. I scan my PC for viruses and spyware at least once a week, and my firewall is always up. I pay attention to all programs that initiate outbound connections, and monitor inbound events on a regular basis. Not everyone will understand all the terminology in Comodo, but it isn't difficult to work out when a program is dodgy or not. Google is your friend, and most spyware and trojans often have very obscure names. Keeping to a routine like this doesn't take up much time, if any at all, since most of these programs can be scheduled to run whenever your PC will be free. In addition to all of that, NoScript, although quite annoying at times, blocks off a lot of elements in webpages and so keeps you fairly safe when browsing (unless you enable all content on dodgy websites, at which point your security routine will come into its own).