Two-sided platforms carry a much heavier fraud burden compared to single-sided retailers. Every buyer, seller, renter, and payer is a potential attack surface, and one bad actor can hit both sides of a transaction at once.
For commerce marketplaces and peer-to-peer (P2P) platforms, fraud protection functions as trust infrastructure, determining whether people keep transacting on the platform at all. If you get it wrong, you lose both the buyer who got scammed and the seller who watched a chargeback wipe out their payout.
Why two-sided platforms face a different fraud problem
A traditional retailer controls the inventory, the pricing, and the checkout flow. But a marketplace or P2P platform controls almost none of that. Sellers list their own items, set their own prices, and message buyers directly. Buyers fund payments, request refunds, and rate transactions. Every one of those interactions is a place where a fraudster can insert themselves and the platform is on the hook for the outcome either way.
That structural exposure shows up in the data. According to the Merchant Risk Council’s 2026 Global eCommerce Payments and Fraud Report, 64% of merchants report a meaningful increase in first-party misuse, including 25% who say it increased by 25% or more, a signal that the problem is accelerating rather than leveling off. For Trust and Safety teams, that means the fraud you stopped last quarter is rarely the fraud you will see next quarter. Fraud rings adapt quickly to marketplace-specific mechanics, including reputation systems, escrow timing, and payout schedules, in ways that generic e-commerce fraud never has to.
The fraud patterns hitting marketplaces and P2P platforms hardest
A handful of attack types show up again and again on two-sided platforms, and they rarely arrive in isolation.
Account takeover (ATO) is the entry point for most of them. A fraudster who compromises a seller account inherits that seller’s reputation, review history, and payout method, and can then use it to run scams that look legitimate to buyers and to the platform’s own detection systems. Deloitte’s analysis of Federal Trade Commission data in 2025 found that P2P fraud drove an estimated $8.3 billion in losses in 2024, with that figure projected to climb to $14.9 billion by 2028 as digital criminals move more of their activity onto peer-to-peer rails.
Triangle scams, also sometimes referred to as triangulation fraud, involve three different parties: a scammer, an innocent third-party victim, and a final target. They work by a fraudster listing an item they don’t own, collecting payment from a real buyer, then using that money to purchase the item from a legitimate third-party seller and ship it to the buyer, closing the loop just long enough to build a fraudulent reputation before disappearing with future payments.
Refund and policy abuse, fake or counterfeit listings, and money muling through P2P transfer rails round out the list. Each one exploits the same underlying weakness of trust extended on the basis of incomplete information about who is actually on the other end of the transaction.
Why generic, single-sided fraud tools fall short
Most fraud tools were built to answer whether a card-not-present transaction is legitimate. That framing assumes a single buyer, a single merchant, and a single checkout event. Commerce marketplaces and P2P platforms need a much broader set of answers. They need to confirm a seller’s identity, detect whether an account has been taken over since its last login, recognize when a listing is part of a broader pattern of coordinated abuse, and flag refund requests that match known policy abuse behavior.
Tools designed for single-sided retail typically cannot connect signals across both sides of a transaction, which means they miss the fraud rings that operate as both buyer and seller across dozens of linked accounts. They also tend to apply friction indiscriminately, slowing down a platform’s trustworthy sellers with the same manual review queues built for first-time, high-risk buyers. In a marketplace where seller retention and buyer conversion both depend on speed, that kind of blunt friction negatively impacts the platform.
What fraud protection built for marketplaces looks like
Effective fraud protection for two-sided platforms starts by assessing thousands of signals across the full user journey, rather than just the moments around checkout. That includes device and behavioral signals at account creation, listing and messaging behavior throughout the seller lifecycle, and payment and payout patterns at the point of transaction.
Sift’s AI/ML-based fraud prevention platform is built around that full-journey view.
Account Defense identifies compromised accounts and takeover attempts before a fraudster can exploit a seller’s established reputation.
Payment Protection evaluates transaction risk across both the buyer and seller side of a payment, which matters when fraud rings hold accounts on both ends.
Authentication adds a step-up challenge, like a one-time passcode or login confirmation, at vital moments, such as onboarding a new seller or releasing a payout.
Underneath all of it, Sift assesses those signals and aggregates them into a Sift Score, a 1-100 rating where 1 indicates a trustworthy interaction and 100 indicates a likely-fraud interaction. Trust & Safety teams use that score inside Workflows and Queues in the Sift Console to route decisions automatically, whether that means approving a transaction outright, sending it to manual review, or applying Dynamic Friction that requests additional authentication only when the risk signal actually warrants it. Insights gives analysts the pattern-level visibility to spot emerging fraud rings before they scale across the platform.
Balancing trust and growth on two-sided platforms
The hardest part of marketplace fraud protection is stopping fraud without punishing the buyers and sellers who make the platform work. A Trust and Safety program that treats every new seller like a suspect will lose sellers to a competitor with a smoother onboarding flow. A program that treats every fraud signal the same way, regardless of severity, will bury analysts in low-value manual reviews while missing the coordinated rings that matter most.
Risk-based Friction solves for that balance by scaling the authentication step to the actual risk level of the interaction rather than applying a fixed rule to everyone. A returning seller with years of clean transaction history should move through checkout and payout without interruption. A new account exhibiting device, behavioral, and network signals consistent with a known fraud ring should face real scrutiny before money moves.
Getting that calibration right is what lets commerce marketplaces and P2P platforms grow transaction volume and trust and safety maturity at the same time, rather than trading one for the other.
If you’re operating a commerce marketplace or P2P platform that’s experiencing a fraud problem, then consider using Sift. Sift utilizes advanced artificial intelligence and machine learning technology that identifies and stops fraudulent activity in its tracks before it can cause financial harm to your platform. If this sounds like something your team could use, consider trying Sift. Request a free demo today.
Frequently asked questions
What makes fraud protection for marketplaces different from standard e-commerce fraud prevention?
Marketplace and P2P platforms have to assess risk on both the buyer and seller side of every transaction, since either party can be the source of fraud. Standard e-commerce fraud tools are built around a single merchant and a single buyer, so they miss coordinated fraud rings that operate accounts on both sides of the transaction, along with marketplace-specific patterns such as triangle scams and seller account takeover.
How does account takeover fraud affect marketplace sellers specifically?
When a fraudster takes over a seller account, they inherit that seller’s reputation, review history, and payout details, which lets them run scams that look legitimate to both buyers and detection systems. That is part of why account takeover has become one of the more costly attack vectors on P2P platforms, contributing to the billions of dollars in P2P fraud losses reported by Deloitte’s analysis of FTC data.
Can fraud protection reduce false declines for trusted sellers and buyers?
Yes. Fraud protection that uses Dynamic Friction applies additional authentication only when risk signals warrant it, rather than applying the same review process to every account. That lets platforms fast-track transactions from established sellers and returning buyers while directing scrutiny toward accounts and transactions that actually show signs of risk.
