In the battle against ad fraud, some of the basic recommendations to protect ad dollars within the programmatic space is to employ a block list so that ads don’t get served from IP addresses associated with fraudulent activity. This recommendation has been stressed to both the demand and supply sides of the programmatic ecosystem. Here are five questions to ask about a block list before applying it to your space:

How often is the list updated?
A static list, no matter how good its creator is, will become more and more obsolete as time rolls on. Yes, a set block list may provide protection against historically bad actors, but the keyword here is “historic”. Ad fraudsters are not able to skim billions from the digital advertising industry by standing still. Ad fraud moves and morphs constantly. A block list can be rendered out-of-date in a short period of time without constant upkeep and maintenance. Companies that rely solely on a static list are leaving themselves open to fraud.

What is the list blocking?
Users of a block list should be aware of what the list includes and why. How does an IP make it on to the list ( i.e., what is the logic that deems it fraudulent)? What does the list protect against? Does it only contain known data centers? Does it include IPs from compromised devices? 

How big of a pool is the list being pulled from?
How big of a picture does the block list’s creator see of the digital ecosystem? If data is pulled from just a small fraction of the proverbial pie, fraudulent IP addresses outside the scope of the creator can easily be missed.

How easy is it to update the block list?
If you are applying a third-party block list to your environment, you should consider whether automated access (e.g., API access) is available, or if you have to manually request the list or download it on your own. Having an automated process saves time and ensures the most up-to-date list is being used.

Can you host the block list within your space?
Having to connect to a block list hosted by a third party can add latency to your bidding process. You should be able to integrate a list directly into your environment.

Block lists can be a tremendous help in filtering out fraudulent traffic, especially within environments that see a lot of traffic (e.g., SSPs, DSPs, Exchanges, and networks), but users should do their homework and ask questions because not all lists are created equal.