Types of Ad Fraud in Paid Advertising

Independent measurement keeps landing in the same uncomfortable range. Pixalate, an MRC-accredited fraud measurement firm, put global invalid traffic in Q4 2025 at 23% of web ad traffic, 36% of mobile in-app traffic and 21% of connected TV traffic, based on more than 103 billion analyzed impressions. Juniper Research's forecast points the same direction: $84 billion lost to ad fraud in 2023, heading toward $172 billion by 2028. Two things follow for a working advertiser. First, invalid activity is common enough to plan for: on some channels it is a fifth to a third of everything measured. Second, the mix varies sharply by channel, so the defense that protects your search spend says nothing about your in-app or CTV exposure. Averages also hide variance between accounts: a niche with motivated competitors can run far above any benchmark while a quiet one runs below.

Invalid clicks made with no genuine interest (by bots, click farms or competitors) to waste budget or exhaust competitors. It shows up as clicks without conversions and repeat activity from suspicious sources.

This is the type paid-search advertisers feel most directly, because every invalid click is a line item: you paid for it, it sits in your reports, and it dragged your conversion rate down on the exact keyword you care about.

Non-human visits from crawlers, scripts, proxies and datacenters, plus low-quality sessions that aren't real prospects. It inflates traffic and engagement while never converting.

Bots are the raw material of most other fraud types: the same automated infrastructure that inflates traffic counts also clicks ads, fills forms and fakes video views, which is why bot detection sits underneath every other defense.

Fake conversions and junk leads (bot form-fills, spam sign-ups) that pollute your CRM and train automated bidding on garbage. The tell is duplication, odd timing and leads that never progress.

Its damage compounds quietly: once fake conversions enter your history, Smart Bidding treats them as success and steers future budget toward more of the same traffic.

Fraud on the supply side: ads served on fake or low-quality placements, hidden or stacked ads, and domains that misrepresent their inventory. It wastes impressions and spend on inventory no real person sees.

A related drain is made-for-advertising (MFA) inventory, sites built to host ads rather than serve readers. An Association of National Advertisers study of $123 million in programmatic spend found MFA sites captured 15% of spend and 21% of impressions, with at least $13 billion in estimated avoidable waste across the industry.

Manipulating attribution to claim credit for conversions, such as cookie stuffing or click injection, so budget is paid out for outcomes the fraudster didn't drive.

It rarely shows up in traffic quality metrics at all; the clicks and conversions are real. The fraud lives in who gets paid for them, so you find it by auditing payouts rather than sessions.