Last month, I was reviewing a Google Display campaign for a client when I noticed that something didn't add up. The placement report showed thousands of impressions across what looked like legitimate news sites, but when I dug into the actual domains, half of them didn't exist anymore. We'd been paying for ads on digital graveyards. Once we spotted it, we immediately excluded the placements and tightened up the placement targeting.

It's a pattern we see too often. Google Display Network promises reach and efficiency, but its automation also creates gaps for fraud to slip through. Research from PPC Shield found that UK businesses lost £186 million to fraudulent clicks in 2025 alone, with 40% of all PPC campaigns hit by some form of click fraud.

For brands running display campaigns, whether that's Google Display Network, Display & Video 360, Amazon DSP or The Trade Desk, understanding ad fraud isn't just about protecting budget. It's about making sure the data you're using to make decisions is actually reliable.

Not all sectors are hit equally

The UK data shows financial services face the worst of it, with 53% of campaigns experiencing fraudulent clicks. Retail isn't far behind at 47%, and real estate sits at 42%.

But it's not just the obvious targets. We work with education, B2B, and public sector clients, and fraud shows up differently depending on the sector. Education campaigns often see suspicious traffic spikes around open day season - spikes which don’t lead to conversions. For B2B clients, we've caught bot traffic pretending to be executives from target companies.

The patterns are usually obvious in hindsight. Sudden spikes in clicks from unexpected locations, high engagement but zero conversions, or traffic arriving at 3am. But if you're not actively looking, they just blend into the noise.

When automation works against you

Google Display is brilliant for reach, but it's also vulnerable. Whether you're running standard Display or Performance Max with display placements, you're letting Google's algorithm find placements automatically. That means less visibility into where your ads actually show up.

Last quarter, one campaign was showing strong impression numbers but terrible conversions. When we audited the domains, we found ads running on Made-for-Advertising (MFA) sites - content farms churning out AI-generated articles designed solely to host ads. They have just enough traffic to slip past basic filters, but the quality is worthless. Fortunately, we caught this early on and excluded a number of MFA sites and similar placements. We applied this change across the account so it wouldn’t happen to future campaigns.

According to IAB UK research, at least £23 million of the £7.3 billion spent on UK display ads in H1 2019 alone was potentially intercepted by fraudsters. And that's just what was measurable.

The principles here apply equally to other programmatic platforms like Display & Video 360 or The Trade Desk, but we'll focus primarily on Google Display Network since that's where most businesses start.

What digital ad fraud actually looks like

• Click fraud is the most common. Bots or click farms repeatedly click on ads to drain budgets. Particularly common in competitive local service industries where competitors might want to exhaust your daily budget before lunch.
• Domain spoofing is more sophisticated. Fraudsters impersonate premium publishers to make rubbish inventory look valuable. You think you're buying placements on The Guardian, but you're actually appearing on a spoofed domain copying their branding.
• Pixel stuffing and ad stacking are sneaky. Your ad gets loaded into a 1x1 pixel frame that's invisible to users, or multiple ads are layered so only the top one shows. Either way, you're charged for impressions that never had a chance of being seen.
• Mobile app fraud is the fastest-growing type of fraud, with invalid traffic rates on mobile significantly higher than desktop. Fraudsters have gotten very good at SDK (software development kit) spoofing and device ID manipulation.

Red flags worth watching

Geographic anomalies are usually the first clue. If you're targeting the East Midlands but getting significant traffic from data centres in Eastern Europe or Southeast Asia, something's wrong.

Engagement metrics that don't make sense are another giveaway. A 15% CTR with a 95% bounce rate and three-second session duration? That's bot traffic.

And when Google Ads is reporting 5,000 clicks but Google Analytics only shows 3,200 sessions, the difference is likely invalid traffic that got filtered out. (It’s worth noting that this can also be due to cookie consent options).

What we actually do about it

Fraud detection isn’t a one-time audit. It has to be continuous. Here’s what we do (these principles can apply to other programmatic platforms, too):

• We maintain constant human monitoring of placements.
• We don’t just rely on platform data, but first-party data too.
• We monitor reports frequently to ensure potential issues are caught early.
• In specific cases, we’ll also look at using third-party tools that can help identify ad fraud.

Always keep an eye on your campaigns

With the right monitoring and controls, you can significantly reduce exposure to ad fraud whilst still benefiting from Google Display Network’s reach. It just requires a bit more of a deliberate approach, rather than the “set it and forget it” mentality. At RKH, we have the team and the tools to prevent and detect digital ad fraud, protecting our clients from wasted budget and reputational damage.