Real Examples of Spammy Comments
Spam comments are often generic and unrelated to the post. They often link to questionable and offensive content so it is important you remove it fast. Links from your blog to porn, gambling, prescription drugs, malware and other potentially dangerous websites can hurt your ranking with Google unless you work diligently remove the links from your blog. You don't want Google labeling your blog as unsafe.
WordPress gives you the capability to moderate your comments before they are viewable on your blog. The discussion option allows you to set your account so comments don't appear until approved by you. This is the most effective way to keep spam comments from appearing on your blog.
WordPress Discussion Settings
While moderating all comments is most effective it is not the best use of your time. To help save you time dealing with SPAM comments you can use a SPAM protection plug-in, such as Akismet. SPAM protection plug-ins check all comments against a database of past SPAM comments and delete spam comments or trackbacks so you don't have to. Most SPAM protection plugins allow you to block email addresses, websites or IP addresses to improve SPAM prevention efforts.
Use a CAPTCHA plugin such as reCaptcha, Comments Captcha Box, or Si Captcha Anti-Spam to prevent the use of Automatic Blog Commenting software. Some automated software will show the user the captcha image and allow them to type in the letters but this is still a deterrent for spammers.
SPAM protection will be something you want to stay on top of and it is worth the effort. Spammers can be both creative and persistent in their attempts to get backlinks from your blog to the websites they are promoting. Not all links in comments or trackbacks are SPAM. Use a SPAM protection plugin, a Captcha plugin, and moderate your comments to be sure they are the type of comments and links you want associated with your website.