Users who have not changed their password since September 12, 2012--when ArenaNet introduced password blacklisting on its servers--will be required to change their password from February 7, 2013 if they wish to continue playing.
Gamers are being encouraged by ArenaNet to change their passwords as soon as possible, however.
ArenaNet introduced password blacklisting, which stops users from choosing passwords that hackers have attempted to use in the past, went active as part of a major security update last year. Guild Wars II suffered from security problems at launch, and ArenaNet has been working to combat the situation since.
Speaking in September, ArenaNet president Mike O’Brien explained the password blacklisting process in detail. "We're building a blacklist of all the passwords that hackers are scanning for--it’s already at 20 million passwords and growing--and we’re preventing new customers from choosing any of those passwords," he said.
"This system has substantially eliminated hackers' ability to steal new accounts, as all new accounts now cannot possibly match what the hackers have been scanning for. The rate of account hacking was about 1.5 percent for accounts created before this blacklist was in place, and is about 0.1 percent for accounts created after."
"Because this has been so successful at protecting new accounts, we want to extend it to protect existing accounts too. But it’s harder for us to know whether passwords of existing accounts are known to hackers: it’s difficult to distinguish between a login attempt by the real customer and a login attempt by a hacker. So we'll take the safe approach and ask all existing customers to change their passwords, and blacklist everyone’s old password in the process."
For more information on Guild Wars II, check out GameSpot's previous coverage.