Click-Fraud: the practice of repeatedly clicking on an advertisement hosted on a website with the intention of generating revenue for the host site or draining revenue from the advertiser
Ad-Fraud: defined as any deliberate activity that prevents ads from being served to human users. No matter the cause – illegal bot activity, historically fraudulent URLs, specific page-level fraud

HIGHLIGHTS:
• Click-fraud can be as simple as one person starting a small Web site, becoming a publisher of ads, and clicking on those ads to generate revenue
• Much larger-scale fraud also occurs with a run of scripts which stimulate a human clicking on ads in Web pages
• Fraud has evolved over time, but right now the most concerning fraud is in the digital video space because of the high CPMs

4 methods on how they make money:
1. A common approach is traffic sourcing, in which a publisher signs up – usually unwittingly – with a fraudster
2. Ghost sites, in which fraudsters essentially eliminate the publisher from the equation
3. One of the most straightforward-yet-detailed methods, is masking a websites true URL address where the ad will actually appear
4. Hiding ads – pixel stuffing and ad stacking

A couple of good resources to understand the why & how of click-fraud / bot traffic:
Adweek: Ad Fraud
Bots Will Cost Digital Advertisers $7.2 Billion in 2016
Click Fraud: Are Bots Eating Your Ad Budget?
What is click fraud and how can you prevent it?
How much of your audience is fake?

Fighting online ad fraud: a couple of tech platforms that are helping us fight fraud – and stay brand safe.
Forensiq
Integral Ad Science

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