Computer Help and Support

Fyi most of the reports of email being hacked are not really true, spammers routinely fake the "From" address in email messages making it look like they've gotten control of your email account.

If the only evidence for the account having been hacked is email that was sent "from" their email account, before believing the worst, you need to examine one of the messages "raw headers" and check the "Received" lines and "Message-ID" lines and take a very close look at the "From" and "Sender" lines and see if the message was actually sent from a Yahoo computer.

I get messages every day from spammers pretending to have sent from my email account. So far, they've actually all come from machines outside the US or malware-infected systems being used as spam-bots.

Of course, changing passwords on yahoo and running malware scans on whatever computers they're using is never a bad idea.

Edit to add: unfortunately reviewing and understanding the "raw" and normally hidden email headers is a bit of an art form. When you first encounter them they can seem a bit complex. It's best to get some help as needed to figure it out.