If you’re an investor, you probably enjoy the convenience of managing your accounts online. But you’ll also want to make sure that you’re not making it convenient for hackers, “phishers” and others with bad intentions to gain the same access.

Fortunately, there’s a lot you can do to protect your privacy. Here are a few suggestions offered by the U.S. Securities and Exchange Commission:

• Use a strong password or passphrase. You’ll want to pick a password that would be virtually impossible for anyone to guess, employing capital and lowercase letters, plus symbols and number...