With millions of websites sending ad inventory into the programmatic marketplaces, it's difficult to quickly determine the quality of traffic from any domain without closely monitoring the impressions. However, there are some tell-tale signs that should act as a warning that a domain's traffic will be less than premium.

1.  It was born yesterday.
A publisher coming to a network with a domain that was recently registered, maybe a few days ago, and the site is pulling in thousands of visits a day - this should set off some internal alarms. Legitimate websites normally take time to cultivate and attract real traffic. 

2.  The domain registration information is hidden behind a proxy service. 
While there are some legitimate reasons for hiding the true identity of the person or entity that's behind a domain, fraudulent sites (e.g., ghost, pirate, phishing, malware-laden, etc.)  often use either a privacy or proxy registration service or information that can't be traced to a real person or company (e.g., fake name, address, and a contact email linked to a free email service) to shield the identity of the site owner. In contrast, premium publishers use their real information.

3.  The domain's content relies heavily on widgets and RSS feeds.
When operating fraudulent sites, the main objective is to create pages as quickly and effortlessly as possible. This often results in pages using RSS feeds of other news and entertainment sites, making it look as though it has real, updated content when it’s actually just showing content from other sites (along with a lot of ad placements).

4.  The traffic volume skyrockets overnight.
Looking at graphs of traffic volume progression fraudulent sites often show steep inclines instead of a steady rise like that of a legitimate site. Sharp rises are tell-tale signs of bot traffic being directed to a site. In some instances, you'll also see an ark-like distribution of traffic where it drops as quickly as it started - a sign bot traffic was turned off.

5.  Sites have a high ratio of ads to content.
Domains with pages that have high ratios of ads versus content should be closely scrutinized. These sites are overly saturated with ads, often to the point where the page content is undiscernible from the ads. Many also include an endless scroll of ads at the bottom of the page that will never be visible to a reader- a telltale sign of a problem domain.  

6.  The URL is very close to that of a legitimate domain.
Fraudsters are known to create URLs that closely mimic premium sites. For example, a real news publisher may use the domain "premiumsite.com" and a fraudster then creates the domain, "premiummsite.com" or "premiumsite.com.co". A quick scan of activity logs can miss these imposters.