How does one get rid of people on yahoo who's accounts are only there to spam or to spread viruses?

i often come people/accounts on yahoo for every question they have the same answer with a link to a site that wants advertising or spreads viruses, i always try to report every answer they have but i don't know what else someone can do to get rid of these accounts/people. do you think there should be a on on some ones account were you can report them to yahoo as well as being able to report individual answers? i mean some of these people have no decency, i came across one just now with a link to a /attack site and once on a question about getting and abortion after some one advertised their shopping website which was completely inappropriate. what else apart form reporting individual answers and questions can one do to stop these people?