A Former Hacker’s Guide to Boosting Your Online Security

Ngô Minh Hiếu was once a fearsome hacker who spent 7 1/2 years incarcerated in the U.S. for running an online store that sold the personal information of about 200 million Americans. Since leaving prison, Hiếu has become a so-called white hat hacker, attempting to protect the world from the sorts of cybercriminals he once was.

These days, Hiếu said, it doesn’t take much hacking to access sensitive details about Americans. Companies and governments routinely leave databases exposed online with little or no protection, as we’ve reported, giving cybercriminals an easy...