Someone has been sending spam from your email account

Your friends have been receiving spam email apparently from your Yahoo/Gmail/Hotmail/etc address?

What does this mean?
At least one of three things may be going on:

1. Your email account may be compromised. In other words a spammer has gotten a hold of your account password and is using your account to send spam to your contacts,
2. A virus/malware has infected one of the computers you use login to check your email and is accessing your account, or
3. A spammer is using an email list that has both our addresses in it and just happened to faking an email from you

What to do?
Although #3 is the most likely (and is actually quite common) you should:

• change your email account password ASAP just to be safe
• make sure your computer has the latest updates (whether Mac, Linux, or Windows). Eg run the Windows update to make sure everything is up to date
• if you have a virus scanner, make sure it is up to date
• scan your computer for viruses/malware
• speak with whoever is in charge of the computers at your work or other place you check your email from about a possible infection