Looking at old Flippa auctions that I scraped, it would be interesting to determine if domains are parked. I found this post, which describes a few options, including checking DNS entries for redirects, finding a blacklist, or content inspection. Some people have built APIs, but none appear maintained, and DNS providers rate limit whois lookups. Google also has an internal, proprietary method for doing this.
I’ve compiled a list of text included in parked pages. I found that GoDaddy is a very common domain parker, and encompasses most of the results in my dataset, but the others are useful too. Many hosting companies operate through common providers, so the text often follows a pattern. A portion of parked sites sell their traffic to third parties, often “mom” sites – these can’t be detected through this method. If you find a parked domain that doesn’t match one of these strings, please comment below!
Identifying parked domains (buydomains.com)
The domain outfit.com is for sale. To purchase, call BuyDomains.com at +1 339-222-5147 or 866-836-6791. Click here for more details.”
Afternic:
This domain is for sale. Click here for more information.
Sedo:
This page provided to the domain owner free by Sedo's Domain Parking. Disclaimer: Domain owner and Sedo maintain no relationship with third party advertisers. Reference to any specific service or trade mark is not controlled by Sedo or domain owner and does not constitute or imply its association, endorsement or recommendation.
GoDaddy:
This page is provided courtesy of GoDaddy.com
NTCHosting, and other hosts (NTCHosting and astmonastir.com vary):
NTCHosting has registered astmonastir.com for one of its customers.
Suspended pages hosted on cPanel hosts:
This page has been suspended
LiquidNet (and many others):
LiquidNet Ltd Hosting has registered valuesalesdirect.com for one of its users.
Domains that are listed “for sale”, for the right price:
"The domain back.in may be for sale. Click here for details." "The domain back.in is for sale. Click here for details."
DNS設定が見つかりません! / DNS ERROR!
I’m not sure which company the source host is for this one, but it’s very common. These two strings are included in a Javascript script block.
http://cdn.dsultra.com/js/registrar.js registrar_frameset