The challenge with cyber-attacks in our current age is not if they can be stopped, but safeguarding yourself from them happening again.
An interesting read over at Heritage.org examines who may have been behind the attacks, and what their motives may have been in doing so. It may be months or years, if ever, to definitively figure out who or what was behind these attacks.
No visible culprit is not a reason to sit back and do nothing. Take the necessary steps to ensure your information is properly secured. Pictures of grandchildren are just as important as sensitive business records or the next "Great American Novel" you have saved on your computer, and the easiest way to keep those documents safe is to be proactive and informed about the measures you utilize to keep that precious information secured.