Spammer stole my Yahoo email and sent out spam mails

Friends, in case you received an email selling you Viagra online, which appears sent from my Yahoo email. I apologize. Obviously I don’t sell those. Some hackers used my Yahoo email and did this. Please ignore that mail. More information (prevention tips) about this tactic can be seen at:

I had my email account hacked into and emails sent out.?

I realized this problem as my Gmail acct is also in my Yahoo address book. Also, one friend asked me “huh”? I think this is not really brand new tactic, and I believe most people already know it. This note is just in case.