Not sure what hidden messages your talking about but Carbonite does send info through chat to other Carbonite users to relay info to them.
And you where not hacked by Carbonite or any addon from this site.
Addons can not hack you. They only run when WoW is running and can not run outside of WoW or communicate outside of WoW.
Chances are you where infected by a keylogger or went to an un-official WoW phishing website. There has been a large amount of phishing emails going around telling people their accounts where hacked. Clicking the links take you to real looking sites that steal your info.
Once hackers get your info it typically takes months before they use it.
Some suggestions.
Make sure Windows Firewall is running or at least get one from somewhere if you don't want to use the free Windows one.
Make sure you Anti-Virus is up to date or if you don't have one install one. Check with your ISP as they may offer a free subscription to a Security Suite to protect your computer. I'm with Comcast and the offer free Norton Protection which also has a firewall.
Run a Malware/Spyware program to see if your infected.
BE VERY CAUTIOUS of ANY email saying your account was hacked. I get about 4-6 phishing emails daily. I use Thunderbird to retrieve my emails and if I highlight a link it tells me it's real destination in the lower left part of the window. Be carefull as some phishing website have names that look VERY similar but are not. They do thing like swap a letter around and replace letters with numbers. If you get a email saying you where hacked try logging into WoW first. If you where hacked then you won't be able to get in. Also to get to your Blizzard account goto Blizzards website directly .. never click links.
Periodically change your passwords. This way if someone got your info they may not be able to use it in time.
Don't give passwords/logins to anyone ...
Get a Blizzard Authenticator. Worth every penny. It will add a very hard to hack layer of security onto your Blizzard account. Have an iPhone/Ipod Touch ... then get the free Authenticator app from the app store. Also other phones and carriers can get an app too but tey charge a few dollars. Authenticator info
HERE
Be safe. WoW is popular and because of this it is highly targeted.
Some suggestions for free Firewalls, AV and Malware protection.
Firewalls:
Zonealarm
Comodo Believe it also does Anti-Virus
Anti-Virus:
Windows Security Essentials Also does Spyware and Malware protection
AVG
Avast
Malware:
Malwarebytes
Spybot Search & Destroy
Hijackthis A little note on this one. This is for advanced users only. It does not remove anything it just creates a log of everything. This log can be looked over on various forums by advanced users to see if anything may be affecting you. They will tell you the steps on how to remove any infection. Typically these people are very friendly and very helpful.
Hopefully this helps a little.