When you get your email, you can click on the box beside them, then press the spam button towards the top of your screen. Doing this will start to build up what YOU think of as spam, as well as what Yahoo has already determined to be spam. This allows you to get rid of items that you KNOW to be spam without opening them. Sometimes, the mere fact of opening a bad email can cause you problems.
You will probably want to periodically go through your spam and your bulk folder to make sure that nothing was accidentally diverted there.
Log In To Your Yahoo Mail Account.
Click on "Options" in the top left corner and click on Mail Options.
Under "General," scroll down until you see the options for Spam Protection. Make sure that the option reading "Automatically move spam to Spam folder" is checked.
Block addresses. Click "Blocked Addresses" under Advanced Options and add any email addresses that you have gotten spam from in the past.
Add filters. Add filters so that emails containing certain words, names, or phrases are automatically placed in the spam folder. You can also make sure that any emails from a certain name are placed in the spam folder.