If you're a Gmail user, consider a stepped-up level of security called two-step verification. When you sign up for this, you'll need both your regular password and (periodically) a code that arrives on your phone.
"This campaign, which appears to originate from Jinan, China, affected what seem to be the personal Gmail accounts of hundreds of users," Google says, "including, among others, senior U.S. government officials, Chinese political activists, officials in several Asian countries (predominantly South Korea), military personnel and journalists."
You may not fall into the category of human-rights activist or government official, but virtually any user of online communications faces similar threats.
