Lesson 6 of 8 · 9 min read · intermediate
Made-for-advertising sites and traffic arbitrage
MFA sites and arbitrage are often not illegal, yet they drain budgets. Learn how they work, the ANA's findings, and grey tricks like ad stacking and lead fraud.
Not every way to waste an ad budget involves a bot. Some of the biggest leaks come from real websites, real visitors and real ads, arranged so that almost nobody benefits except the site owner. The best-known example is the made-for-advertising sites site, usually shortened to MFA. Closely linked is traffic arbitrage: buying visitors cheaply and reselling their attention to advertisers at a higher price.
Imagine a "magazine" with one sentence per page and ten adverts around it, handed out free at a train station by people paid per copy handed out. Every copy is real and every reader is human, but nobody is actually reading. Advertisers who pay per page viewed are technically getting what they paid for, and still getting almost nothing.
What makes a site "made for advertising"
The ANA, together with industry groups, described MFA sites by a set of typical traits rather than one rule. Common signs include:
- A very high ad-to-content ratio, with ads crowding out the article.
- Fast ad refresh, where ad slots reload every few seconds regardless of whether anyone is looking.
- Slideshow or "listicle" layouts that force a new page, and new ads, for every paragraph.
- Most traffic bought from other platforms, especially social and content recommendation widgets, rather than arriving organically.
- Generic, templated or AI-generated content with little original reporting.
That study, run from September 2022 to January 2023 with 21 ANA member advertisers, covered about $123 million of spend and 35.5 billion impressions. Its MFA finding became one of the most quoted numbers in the industry and pushed many agencies and DSPs to add MFA exclusion lists in 2023 and 2024.
How arbitrage works
- Buy cheap attentionThe site operator buys visits from social ads, native widgets or push notifications, often for a few cents each, sometimes in cheaper markets.
- Pack in adsEach visitor sees many ad slots, refreshed often, across several paginated pages.
- Sell programmaticallyThose impressions are sold through SSPs at display CPMs, frequently via multiple resellers to maximise demand.
- Keep the spreadIf ad revenue per visit exceeds the cost per visit, the operator profits and scales up. Search arbitrage works similarly, with search-style ad units instead of display.
Arbitrage is not automatically fraud. Many legitimate publishers buy traffic to promote their content. The problem is the incentive: when the only goal is ad revenue per visit, quality falls, and the cheapest traffic sources are also where sourced traffic and bots hide. The MRC counts invalid incentivised promotion and hidden ads as SIVT, but a merely cluttered site is not IVT.
MFA and aggressive arbitrage
- Real humans, real pages
- Usually legal and often policy-compliant
- Wasteful: low attention, poor outcomes
- Handled with exclusion lists, curation and SPO
Invalid traffic and fraud
- Fake or hijacked users, or hidden ads
- Breaks platform rules; sometimes criminal
- Worthless: no human saw the ad
- Handled with IVT detection, blocking and refunds
The grey tricks that inflate impressions
| Technique | What happens | Classification |
|---|---|---|
| Ad stacking | Several ads layered on top of each other in one slot; only the top one can be seen, but all are counted | SIVT (hidden or obscured ad serving) |
| Pixel stuffing | A full-size ad squeezed into a tiny, often 1x1, frame invisible to the eye | GIVT when 0x0 or 1x1 is detected; SIVT when disguised |
| Auto-refresh abuse | Slots reloading constantly, including when out of view or in a background tab | Policy breach; IVT if impressions are never rendered or seen |
| Cookie stuffing | Dropping affiliate or tracking cookies without a real visit, to claim credit for later sales | SIVT (cookie manipulation) |
| Lead-gen fraud | Fake or recycled form fills, bots completing sign-ups, or real people paid to fill forms | Fraud; often caught by the advertiser, not the ad server |
Lead-generation fraud deserves its own warning
In insurance, education, loans and B2B software, advertisers often pay per lead. That price can be tens or hundreds of dollars, so fraudsters use bots, form-filling scripts, stolen identities and click farms to fabricate leads. In India, Southeast Asia and the US alike, sales teams discover the problem when they call "leads" who never asked to be contacted. Defences include checking phone and email validity, spotting identical submission timing and cross-checking the traffic source the lead came from.
Why MFA keeps coming back
MFA thrives because automated buying rewards cheap reach. A DSP optimising for the lowest cost per impression, or for clicks, will naturally drift toward cluttered pages with many slots and accidental clicks. After the ANA study, many buyers added MFA exclusions, and some operators responded by making their sites look more like ordinary publishers, reducing obvious clutter while keeping the bought-traffic model. Classification is therefore a moving target, just like SIVT.
The debate is also about fairness. Some legitimate publishers, including many in emerging markets in South and Southeast Asia and Latin America, rely on bought traffic to grow and use heavy ad layouts because CPMs are low. Blunt exclusion lists can catch them alongside the real offenders. The fairer approach is to judge outcomes: attention, viewability, conversion and incremental results per dollar, measured on the same campaign across sources.
Key takeaways
- MFA sites are real sites built to maximise ad impressions, not readers; they waste money but are usually not IVT.
- The ANA's 2023 study found MFA sites made up 21% of impressions and 15% of spend in the campaigns it analysed.
- Arbitrage buys cheap traffic and resells it as ad impressions; the cheapest sources are also where bots hide.
- Ad stacking, pixel stuffing and cookie stuffing are SIVT; lead-gen fraud targets pay-per-lead campaigns.
Questions people ask
What are made-for-advertising (MFA) sites?
MFA sites are websites designed mainly to generate ad revenue rather than serve readers. They typically have many ads, fast ad refresh, slideshow layouts, thin or templated content, and traffic bought from social or recommendation widgets. The ANA's 2023 programmatic transparency study found MFA sites accounted for 21% of impressions and 15% of spend in the campaigns analysed. They are wasteful but usually not invalid traffic.
Is traffic arbitrage illegal?
Usually not. Buying visitors to a site and earning ad revenue from them is a common, legal business model, and many honest publishers promote content this way. It becomes a problem when traffic sources are low-quality or fraudulent, when ads are hidden, stacked or auto-refreshed abusively, or when it breaks platform policies. Buyers manage it with MFA exclusion lists, allow-lists and supply path optimisation.
What is ad stacking?
Ad stacking is when several ads are layered on top of one another in a single ad slot, so only the top ad is visible but every ad in the stack is counted as an impression. The MRC classes it as sophisticated invalid traffic. HUMAN's 2023 VASTFLUX takedown uncovered a large in-app version that stacked dozens of invisible video ads behind visible banners.