Here’s a concise, practical guide to secure online payment processors (what they do, why they’re secure, and which to pick).

Top secure processors / platforms (short pros + security highlights)

• Stripe — very developer-friendly, strong fraud tools (Radar), built‑in tokenization and 3DS support, helps reduce PCI scope via hosted fields and SDKs. Good for SaaS, marketplaces, and scale. (stripe.com)
• PayPal (including Braintree) — huge buyer adoption, hosted checkout options and buyer/seller protection programs; Braintree offers a secure Vault and encryption/tokenization for stored cards. Good for simple checkout and wide customer recognition. (paypal.com)
• Square (Block) — easy setup for online + in‑person, built‑in tokenization, P2PE for card‑present, and Square handles PCI compliance for merchants. Good for small businesses and omnichannel sellers. (squareup.com)
• Adyen — enterprise/global platform with PCI DSS Level 1, P2PE, tokenization, 3DS and advanced risk tools; strong for global merchants and large retailers. (help.adyen.com)
• Authorize.Net — long‑standing gateway with fraud detection tools and formal PCI attestations; often used by merchants who want a separate merchant account + gateway. (support.authorize.net)
• Worldpay / Global Payments (major acquirers) — enterprise-grade tokenization, fraud controls and global acquiring; common choice for large volume merchants. (developer.worldpay.com)
• Shopify Payments / Amazon Pay — convenient if you use those platforms; they handle PCI scope for you and offer platform‑level protections. Good for stores that want minimal payments ops. (techradar.com)

Key security features to check (why they matter)

• PCI DSS compliance / Attestation of Compliance (AoC) — ensure the provider is at least a validated service provider (Level 1 where applicable). PCI DSS is the industry baseline. (pcisecuritystandards.org)
• Tokenization & Vaults — card numbers are replaced with tokens so sensitive PANs aren’t stored in your systems. Reduces breach risk and PCI scope. (squareup.com)
• Point‑to‑Point Encryption (P2PE) / TLS — encrypts card data in transit; P2PE additionally protects data from capture at the point of entry. (pcisecuritystandards.org)
• 3‑D Secure (EMV 3‑DS) / Strong Customer Authentication — reduces fraud and shifts liability in some disputes; important for e‑commerce and cross‑border transactions. (docs.stripe.com)
• Fraud detection & chargeback management — machine learning scoring, rules, velocity checks, and clear chargeback procedures are essential. (docs.stripe.com)
• SOC / ISO certifications and third‑party audits — look for SOC2, ISO27001, and QSA audit statements for added assurance. (help.adyen.com)

Practical selection guidance (pick based on your business)

• If you’re a hobbyist / very small online seller: PayPal, Square, or Shopify Payments — minimal setup and PCI burden. (paypal.com)
• If you’re a developer or scaling startup: Stripe — best APIs, flexible integrations, advanced fraud tools and Connect for marketplaces. (stripe.com)
• If you’re enterprise / global: Adyen, Worldpay / Global Payments, or a full‑service acquirer — broad payment methods, global acquiring, and enterprise risk tools. (help.adyen.com)
• If you need a gateway + existing merchant account: Authorize.Net or Braintree (if you want PayPal ecosystem). (support.authorize.net)
• If you run a marketplace/platform: use Stripe Connect, Adyen for Platforms, or similar platform offerings (they handle KYC, payouts, and reduce regulatory burden). (stripe.com)

Costs & contract items to watch (security‑related)

• Fee model (interchange‑plus vs flat rate) — affects total cost at scale. (business.com)
• Liability/chargeback rules and who bears fraud losses (platforms vs sellers). (guardyourconnect.com)
• Data retention, breach notification, and incident response SLAs — ensure the provider commits to timely notification and support. (Ask for AoC / SOC reports.) (support.authorize.net)

Quick setup checklist (minimum to be secure)

1. Choose a provider that publishes a current PCI AoC or PCI status and SOC/ISO reports. (support.authorize.net)
2. Use hosted fields/checkout or client SDKs so your servers never see PANs (reduces PCI scope). (stripe.com)
3. Enable tokenization and store only tokens for recurring billing. (squareup.com)
4. Turn on fraud tools and 3‑D Secure where supported to reduce fraud and liability. (docs.stripe.com)
5. Monitor transactions, set velocity/AVS/CVV rules, and have a chargeback procedure. (braintreepayments.com)

A realistic caution

• No vendor is immune to incidents — always do your own diligence (review AoC, SOC reports, recent security history and public disclosures). For example, large providers have had regulatory actions in recent years; review news and regulatory filings as part of vendor selection. (reuters.com)

If you want a single quick recommendation

• If you can integrate code and want flexibility + strong security: start with Stripe (hosted checkout + Radar + tokenization). For a low‑effort option that’s still secure, choose PayPal or Square/Shopify Payments depending on which storefront you use. (stripe.com)

If you want, I can:

• generate a 1‑page vendor comparison (fees, required PCI effort, best for) for 3–5 finalists, or
• produce the exact list of security questions and documents to request from any processor (AoC, SOC2, penetration test summary, encryption/P2PE details, 3DS support, fraud controls).

Tell me which of those you want and I’ll prepare it (I can base recommendations on your estimated monthly volume and technical resources).