Trion Worlds had to be tipped off by a hacker about a serious security hole that allowed gamers' Rift accounts to be compromised.
Aliased do-gooder ManWitDaPlan raised the alarm, earning himself "heartfelt thanks" from Rift executive producer Scott Hartsman.
An update was rushed out at the weekend to slow the "botnets and hackers" down. Trion Worlds said 1 per cent of the game's population had been affected.
"However, 1 per cent of a surprisingly large number is still very noticeable," wrote Hartsman on the Rift forum.
"The sobering fact is that account security remains a multifaceted issue, as attacks from other sources continue.
"It's important to remember is that while a hole was identified and fixed as rapidly as we possibly could, there are still hackers and botnets trying account/password combinations from compromised web sites and past MMOs.
"They are doing this right now," he added. "Those attacks have been coming constantly since we launched the game.
"The only thing that changes are how many hundreds of computers are trying to get into your account at any given moment, where they're coming from, and how many are succeeding."
With ManWitDaPlan's help, Trion issued a log-in vulnerability fix to rectify a "very subtle" bug with user validation. "No personal information or any such was leaked out," Hartsman promised, "and no outside attacker penetrated our servers, networks, or databases."
Hartsman concluded: "Our staff has been, and will continue to be, working around the clock to get those impacted back in shape. We'll continue hiring on even more people to help people with issues of all kinds, as quickly as we can. (Another round of hires begin on Monday, and there will be even more to follow.)"
Eurogamer scored Rift 8/10 - it's the best MMO you've never heard of.
"Trion has proved that it is possible to produce an exquisitely polished, content-rich MMO from the moment of launch, setting a dangerous precedent for upcoming releases in the process," declared reviewer John Bedford.
"That Trion has managed to meet every expectation set in the past few years, from achievements to fully-fledged crafting and economy, while also bringing a truly innovative feature to the table is a testament to the will and determination that's driven Rift's development."