My brother's hotmail and yahoo mails are hacked.  The hacker has get
hold of his contacts and email content.  The hacker has been sending
unsolicited emails to my brother's contacts, as well as using some of
his email contents to send stuff around.  The hacker also open up
several new accounts (impersonalizing my brother) and send email to
his contacts.  Questions:

1. Is it illegal?
2. What can my brother do?  What proof he needs to get?  He only has
IP address but it seems hard to trace back to the hacker.
Thanks!

Sometimes a service provider can help.

Otherwise, of course, he needs to change accounts (I.e. new names).

And, he needs to install something like Zone Alarm of other proven
firewall.  A home version is free. I think XP Service Pack 2 supplies
one, but I use Linux so am not sure.

Regarding the Hotmail hacking issues, you can e-mail your issue to
"abuse@css.one.microsoft.com". they will get in touch with you and
they will check your identiny and solve your issue.