Info needed.

[REDACTED]

I have a MacBook Pro OS X Yosemite, avast for mac. Web browser is safari. Every thing has the currant updates and I use yahoo mail. My computer is clean and has no viruses or malware.
My issue is my contacts in yahoo mail were accessed and then spam emails were sent to my list.
How can this happen when my defences were already in place?

[specimen9999]

There is no protecion against a user allowing a site to access their contact list, this is normal in sites like Facebook an LinkedIn and we trust them not to abuse this information, but any site, normally a social network oriented one, can ask to access your contacts, has this happen?

[REDACTED]

Thanks for your reply. No linked and Facebook don't have access to my contacts, I do believe its coming from my yahoo account contacts. My computer is protected by Avast for mac also Malwarebytes. Yesterday there was a mass email to my contacts with my email address saying it was sent from my iPhone
with my name on there as well, I've also checked sent mail and its not coming from my account at yahoo? any help will do. Cheers

[Pondus]

change all your account passwords

addresses can be harvested and send from address can be faked
this may not have been harvested from you / your account

http://lmgtfy.com/?q=how+do+spammers+get+my+email+contacts
http://lmgtfy.com/?q=spam+mail+show+sent+from+me+but+it+is+not+me