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Why not block ad bots?

Published June 3, 2019

Some ad fraud tools focus on blocking bots, but there are several reasons not to do this. We explain why.

Invalid traffic (IVT) is a problem for most eCommerce stores. In particular, IVT can cost businesses a lot of money by using bots to deflate an advertising budget through fraudulent clicks, impressions, and retargeting. NS8 flags bots that come to a site and prevents them from making it onto a retargeting list. That prevents additional money from being spent on them. But why not block all bots from seeing any ads at all?


Websites sometimes use a system called caching to make a site run faster. Instead of having to reload a page every time a person asks for it, a server will “cache” the latest version of the site (essentially like a download or saved version) so that it can return it to the viewer faster. Sites do this by having bots run a script to cache the site. If your ads are invisible to bots, they may not appear on the cached version, and therefore potential customers may not see them.


Bots that are not malicious will identify themselves to a website. Sites running ads (particularly programmatic ads) run on JavaScript, which recognizes this identifier. Any impressions or clicks made by these known bots are excluded already by the JavaScript code and should not produce costs for the advertiser. It is only malicious bots that mimic human behavior and fail to identify themselves that will generate costs.

Most ad blocking software does not differentiate between the types of bots, which means that bots you do want to see the ad will be prevented just like the bad bots. This could lead to lower search engine rankings and other unintended consequences. While NS8 can differentiate between good bots and bad bots, not knowing that these bots are viewing your ads may mean that you continue to advertise on sites that are mostly bot traffic. This could lead to reputation issues and other problems.

Known Sources

One way to block just the malicious traffic is to simply stop traffic coming from known sources of fraud from viewing your ad. However, these lists are constantly changing (as fraudsters are constantly adapting), so you may be blocking some bad traffic while letting worse traffic through. In addition, many ad platforms have limits on how many traffic sources you can block. These would have to be constantly updated and would still not be entirely effective.

IP Rotation

Similarly, malicious bots have the ability to change attributes at will to attempt to get through defenses. While a particular IP address may be a known fraud bot, it will likely rotate through multiple IP addresses while attempting to view the given ad. They can also change browser strings and other identifying information in an attempt to get the ad served. Even if 80% of these tries are blocked, each bot will still likely get served some number of ads. You still lose money to the bot, and you have no way of knowing it happened.


Which leads to our last point — information can be valuable. By tracking IVT instead of blocking it, NS8 is able to score specific campaigns to show where invalid traffic is coming from. It can even tie fraudulent orders to the specific campaigns where they originated. This gives eCommerce companies the tools they need to optimize their ad campaigns to reach human users without causing additional problems.

NS8 Protect can help eCommerce companies avoid IVT while maximizing the ROI on their ad campaigns. To learn more, contact our sales department.

Post Author: Jackie Long
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Blog Manager at NS8. With a varied background and over 5 years of content creation experience, Jackie works hard to provide a compelling range of informative articles.