Now would be a good time to refresh your Twitter password. The social network has revealed that there was at least one attack on its servers this week that may have collected email addresses, passwords (thankfully encrypted) and session tokens for about 250,000 users. The real risk to users is unknown, but Twitter raises our eyebrows when it suggests that this was more than just a casual scripting hack: it claims the intrusion attempt was "extremely sophisticated," and that other firms might have been subject to a similar breach. You'll know that you were immediately affected only if you see Twitter send a notice of a forced password reset, like what you see pictured above. We'd be cautious, all the same -- when such attempts seemingly increase in frequency by the day, it's not a bad idea to stay on guard.