Guild Wars 2 developer ArenaNet has said hackers have stolen "lists of email addresses and passwords from other games and web sites and are systematically testing Guild Wars 2 looking for matching accounts."
In a statement posted on the Guild Wars 2 wiki, ArenaNet placed the onus on its players, saying that the vulnerabilities are a result of using the same login details across multiple games.
"To protect yourself, use a strong, unique password for Guild Wars 2 that you've never used anywhere else!" reads the statement. "If your current password isn't unique to Guild Wars 2, change it today! Do not under any circumstances use the same password for Guild Wars 2 as you do for your email account."
According to the dev the information was acquired using spyware and is being used indiscriminately to gain access to non-existing accounts.
"We've observed hack attempts against hundreds of thousands of accounts that don't even exist. To protect those people in case they purchase Guild Wars 2 and create an account, we will now disallow customers from picking passwords that we've previously seen used in a hack attempt."
This is the second attempt at breaching Guild Wars 2's security. Last month a Guild Wars 2 hack attempted to compromise accounts with password resets.