SEGA Japan ID holders received a somewhat troubling email earlier today, informing them that SEGA has suffered a hacking attempt by "malicious third party."
Though the original email was in Japanese, a rough translation reveals that SEGA is currently investigating "unauthorized logins" to several SEGA ID accounts. As such, they're suggesting that users who don't log in regularly should immediately check their accounts and change their passwords. Just in case.
In addition to this warning, SEGA also put together a basic guide on protecting yourself from these sorts of situation. When creating a password, don't use one you've previously used and avoid including personal (or other easy-to-guess) information as part of your password. Additionally, don't reveal your password or SEGA ID to third parties and be mindful of fake emails looking for your private information.
SEGA also discourages users from sharing accounts with friends and family.
For those unaware, a SEGA ID is basically the equivalent to a Battle.net account and used primarily by SEGA Japan. The company uses a different system in North America.
Thanks for the tip, VeGiTAX2.