In Yahoo's case, the compromised account information includes names, email addresses, telephone numbers, dates of birth and, in some cases, unencrypted security questions and answers. These details can be used to impersonate you or to authenticate you on other websites.
Don't provide real answers to security questions, if you can avoid it. Make something up that you can remember and use that as answer. In fact, Yahoo doesn't even recommend using security questions anymore, so you can go into your account's security settings and delete them.
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