Google is in the process of a massive penalty sweep targeting many Private Blog Networks (PBNs) where they have been applying penalties and deindexing sites that are utilizing PBNs.

Private blog networks (PBN) get their name because they are generally controlled by a single person or company and are supposedly harder to trace.  But with the demise of many link networks, more of these supposed “private” blog networks have popped up offering links from within these networks for sale – which people argue takes it from being a private network to a public one. But selling links also makes it much easier for Google to discover.

Unlike many other networks, they generally try and keep their feeder sites limited to only a set number of outgoing links and sites.  This is one of the ways they tend to be harder to detect.  They also use a variety of ways to keep the sites seemingly controlled by a variety of different people by using different registrars, hosting companies, TLDs (ie. they won’t be all .com but also include some .net, .org, and country specific TLDs), different WordPress themes, author profiles, AdSense accounts, ad networks and unique quality content.

With Google’s assault on many public link and blog networks, private ones have become more popular this year.  But private blog networks being penalized isn’t new – but because they are controlled by one person or a small group of people, you don’t hear about it as often as when public blog networks or link networks get hit, when many different people are penalized.   However, this time Google seems to have targeted many different private blog networks at once in a massive crackdown, which makes sense given their increased popularity.

How did Google discover the private blog networks?  As we have seen with link networks who claim Google would never be able to find any footprints, it likely started with the investigation with one site that led to the unraveling of them all.  But people are speculating on several things that could have been seen as footprints:

• Using CloudFlare to anonymize IP addresses across all the domains
• using the same registrar/hosting
• same domain registration info; blocking third-party link analysis tools (such as Ahrefs and Majestic)
• blocking third party link tools by using the same tool
• all use WordPress
• all use the identical set of WordPress plugins without variation
• powered by domains that have been purchased from auction sites
• powered by expired domains
• selling links within the PBN to any site, especially when they buy from multiple networks, not just “quality” ones

Then of course there is always the question of:

• using the same AdSense account
• using Gmail addresses for anything related to PBNs
• using the same Analytics account
• using the same Google Webmaster Tools account.
• sites people include in disavow files that aren’t supposed to have any impact on the sites included, but many wonder when that data will be used.

Many of the sites hit were NOT penalized with unnatural link penalties however, which is what the natural assumption would be for anything resembling a private blog network.  They were hit with thin content penalties for having “thin content with little or no added value”.  However, many people involved in PBNs say that the content was actually well written unique content, and nothing that should be hit with the thin content penalty.

Matt Cutts tweeted about it as well, referring to PBNs as a “blackhat SEO fad”.

Will this be the last of PBNs?  Of course not.  Those who have been penalized are already rebuilding… but many likely won’t be so greedy to sell links without vetting them more carefully, as opposed to the “we will link to any crappy site” that many employ – and that puts it in danger.