Review Your Online Accounts
Next, you'll want to review your online passwords to see whether you are using the same password and login ID across multiple accounts. If, for example, your PSN and e-mail logins are the same, change your e-mail address password immediately.
Many people often use one difficult password across multiple online accounts, because it's easier to memorize just one set of credentials. If that sounds like you, I highly recommend you try a password manager such as LastPass (my personal preference) or KeePass. That way you can use as many difficult passwords as you want without having to memorize all of them. If you use multiple devices during the day such as a laptop, desktop, tablet (iPad or Xoom) and smartphone, you may want to look for a password manager that has software available on all the platforms you use.
For more information on password best practices check out PCWorld's "How To Protect Your Online Passwords."
Consider Two-Factor Authentication
For an added dose of security, you can also use two-factor authentication on accounts that support them. Two-factor authentication basically means your account requires a randomly generated password in addition to your regular password before you can access your account. The second password is usually generated by an extra piece of software, authenticated by you, on a keychain dongle or smartphone app. This makes it harder for hackers to break into your online accounts.
Google recently released two-factor authentication for Google accounts, and Facebook has announced that it intends to roll out the security feature to users. Symantec also provides a free two-factor authentication service called VeriSign VIP Access for Mobile. You can find out more about Symantec's service here, including which websites support it.
When PSN Comes Back
Sony hasn't detailed if it will require extra authentication steps from you the first time you login to PSN after it comes back online. But make sure that you login as soon as the service becomes available and change your password.
When security breaches like this happen, it's best to play it safe and take precautions to safeguard your data in case it has fallen into the wrong hands. And if nothing bad happens to you, at least you took the time to review your online security management practices, which is never a bad thing to do from time to time.