The Jagex Account Guardian feature is a free security option users can enable, allowing them to tie their account to specific computers. Accessing the account from unregistered devices will require a series of additional security questions, protecting users even if their username and password are taken.
"Ensuring the integrity and security of our valued community's information has always been a top priority for us. This recent update serves to strengthen the number of other innovative countermeasures we have developed over the past years" said Jagex CEO Mark Gerhard.
"Our players put a significant investment of both time and effort into their RuneScape accounts, so it's incumbent on us to remain at the very forefront of protecting their investment," he added.
In July the free-to-play game reached 200 million registered users.
Launched in 2001, RuneScape is recognised by Guinness World Records as the world's largest free MMORPG and the most-updated game.