I get spam from the user accounts of people I know who aren’t doing it. How does that happen?

mal7798: I get spam from the user accounts of people I know who aren’t doing it. How does that happen?
I am getting messages for advertisements (spam) from certain people on my Yahoo Messenger contact list, and I know that these people would never do that, and when I ask them about it, they have wondered how to get these to stop. This apparently continues to happen to those who have changed their Yahoo ID passwords. How does this happen, and how does one get it to stop?

Answers and Views:

Answer by Amber
It’s spyware and they need to run a spyware detector/repair program.

I suggest Spybot Search and Destroy. It’s free, you can get it at download.com