I was going to just resteem a post here from @jrswab, but it seems like Steemit doesn't allow resteeming of old posts. That's unfortunate. So here is the link instead:
Great overview of some things we can do to protect ourselves online. Security is a complex topic but this is a big deal, guys. We are all making money here. Maybe not a lot, but with SBD and STEEM both shooting up, even a few upvotes can translate into some money. We are all potential targets of hackers. Take this stuff very seriously.
If time allows I will write more about passwords specifically, or maybe I'll just resteem JR if he beats me to the punch. Either way, look for that post soon. But for the time being, go read the one I link to above.