A friend's yahoo email account sends emails with subjects like:
- This Kit changed all my life
- no regrets after doing this venture
- Look what i found here!
What can he do to about it?
First of all you should check if the sender is not faked (check the e-mail header if it has been sent via Yahoo). If it is not faked your frind should immediately
Your friend's account has, most probably, been hacked. He should take it back immediately by changing his password (if he still can - assuming the hacker hasn't changed it already) and/or notifying Yahoo. See Robert's reply for details.
In case your friend's account has been taken over by a worm or virus, recommend a full computer AV run for him - and do one yourself. You can never know what has been transmitted so far.
You need to block all emails from your friend's address until such time as he has taken it back. Make sure you do not click any links in any emails, or take anything in them as real until such time.