The Guild Wars 2 Wiki warns Guild Wars 2 users that they need to be on the lookout for phishing schemes pretending to be official emails from ArenaNet asking for personal information.
"Account Security Hackers have lists of email addresses and passwords stolen from other games and web sites, and collected through spyware, and are systematically testing Guild Wars 2 looking for matching accounts," reads a lengthy post on the Wiki. "To protect yourself, use a strong, unique password for Guild Wars 2 that you've never used anywhere else!"
The post goes on to offer some advice on how to get your account back if it has been temporarily banned for bad activities such as gold farming. Many of those accounts have simply been hacked and used for nefarious means until ArenaNet finds them and bans them. If you receive a message along the lines of "this account has been permanently banned for a violation of the User Agreement," and you are not a gold farmer, then chances are your account has been hacked. The Wiki offers instructions on how to make things right.