My wife's email account recently sent out spam emails (identical to the ones I've been receiving from Joe and Johnnypark) to people on her Yahoo contact list. My first thought was a virus but after checking into the matter further, it looks like her Yahoo account had got hacked (password stolen). After researching the symptoms it seems a group of hackers has been running a brute force (trying every possible password randomly) attack against yahoo mail and facebook accounts.
Her yahoo mail showed a login from a Polish and Brazilian IP around the time it sent out the spam. The emails usually have a blank or simple subject line (Re:, Hey, etc) and contain a single link to a "Buy Viagra" site or similar. The linked site sometimes tries to run malicious script when visited too.
If you use yahoo/facebook, it might might be a good idea to change your passwords to something more complicated that you don't use anywhere else.
Her yahoo mail showed a login from a Polish and Brazilian IP around the time it sent out the spam. The emails usually have a blank or simple subject line (Re:, Hey, etc) and contain a single link to a "Buy Viagra" site or similar. The linked site sometimes tries to run malicious script when visited too.
If you use yahoo/facebook, it might might be a good idea to change your passwords to something more complicated that you don't use anywhere else.