Apparently, there are spoofers, hackers, whatever…who are sending emails to accounts with the word “Hi” or “Opa” in the subject line, many times with weird symbols surrounding the word. These emails appear to be sent from valid email accounts, but they are not.
Do not open these emails, as they can actually be made to look like they are from someone you know. They contain links to malware sites and other little viruses.
And the rest of the logic applies here too, keep your virus software updated, change your passwords once in awhile…use strong passwords etc… (check with your providers for complete instructions).