SUB DOMAIN SPAM

Sub domains are virtually considered different websites, which are easy and cheap to setup. Just by doing a simple configuration on your server you can make the server understand names like domain1.yourdomain.com, domain2.yourdomain.com. Most of the big sites have sub domains and there is nothing wrong in it. There are many valid reasons to have sub-domains.

Few valid reasons for having sub-domains:
    1. Some websites want to keep their support, products, services etc., separate and then want them virtually on different websites without spoiling their brand. So they have sub-domains to manage their brand since all the name will be ending with theirbrand.com.
    2. Free hosting websites cannot provide free domains which goes for more than 10$ a year. So many free web hosting companies provide free hosting as a sub domain. It's not going to cost them much.
    3. Many blog platforms like blogger, Wordpress uses sub domains to allow people to freely blog without paying for hosting or domain name.
    4. Sub domains for load balancing – Major search engine's huge websites, uses sub domains to redirect users to different servers based on the load on the servers. Google used to have domains like www1.google.com, www2.google.com, www3.google.com. All these domains are sub domains of Google.com and Google uses them for load balancing.
    5. Sub domains for branding and organizing are primarily used by big websites. A typical but valid example is about.com. About.com uses sub domains for various topics. It has domains like searchengine.about.com, cosmetics.about.com that separates them into each site dealing with different topics.

Sub domains and spamming:
    1. Sub domains were abused to great extends when the search engines consider them different websites. People used to create 100s of sub domains like product1.yourdomain.com, product2.yourdomain.com; product3.yourdomain.com, product4.yourdomain.com etc., and cross link them to artificially inflate link power and PageRank which can result in good search engine traffic.
    2. Due to the free availability of sub domains and sub domain blogs search engine spammers create 100s of domains, add some junk content, get links by cross linking or by trading links to impress the search engines and get traffic from them. Most of these junk blogs will be either MFAs (Made for Adsense websites) or not worthy affiliate websites.
    3. Back in 2006 a spammer happened to make Google crawl billions of pages using sub domains and adding contents scrapped from other websites. Google immediately removed and de-indexed the website from their index but eventually a spammer was able to succeed to some extent with his dirty sub domain spam.
    4. Adding keywords in sub domain is easy. If someone registers www.aaayt.com but they want to optimize the website for automobile industry they might want to add their keywords in domain and URL. To make it easy for people to remember sub domains are better choice than sub directories. But a spammer will not go for decent names like auto.aaayt.com or automobile.aaayt.com but he will create sub domains like auto-transport-automobile-cart-shipping.aaayt.com. This is possible in sub domains but is a blatant SPAM in search engine view. A spammer will not stop with one sub domain he will create 100s or even 1000s of sub domains with all the keywords targeting to get traffic from search engines.

Images

The above image shows an example of a site with multiple sub domains cross linking each other and generating spam and junk pages. Google penalizes sites that create 100s and 1000s of sub domains just for the purpose of manipulating the search engines.

This image shows typical tactic of sub domain spamming where, there is a original domain named domain1.com which has its own sub domains interlinked to each other. All these sub domains consists of junk content and stuffed keywords and are cross linked to each other, to inflate the search engine rankings.

Screen Shots

Working Examples

Other site that refer to the same manipulation tactic are as follows

1. Are subdomains bad for SEO?