Think of APIs as the invisible pipes connecting banks, shops, and apps - carrying money and data instantly behind the scenes. Those pipes are so busy (71% of all internet traffic runs through them) that criminals know exactly where to jiggle the valves.

Ways criminals weaponize your APIs

🔑 Credential stuffing - attackers replay stolen username/password pairs directly against login APIs to hijack accounts. They use automated tools plus rotating proxies so requests look like many different users.

🧩 Broken object-level authorization (BOLA) - by tweaking IDs or tokens in API calls, criminals access other users’ data or actions that should be off-limits (think: changing a customer number to view someone else’s orders). This looks like normal traffic, so signature-only defenses miss it. ^[ref]

🤖 Bot automation - sophisticated bots target APIs (not webpages) to automate fraud: bulk checkouts, coupon farming, or mass balance checks. These bots mimic real clients and spread activity across many IPs and devices.

📈 Scraping & inventory hoarding - bots pull pricing, stock and exclusive-offer data at scale to undercut sellers, snatch limited items, or clone catalogs; the business impact is real revenue loss and higher infrastructure costs. ^[ref]

👻 Shadow and zombie endpoints - forgotten or undocumented APIs and old versions often lack modern checks (auth, rate limits), creating easy "side doors" attackers love to probe. ^[ref]

In short: APIs are now the busiest lanes on the internet highway. In H1 2025, researchers logged over 40,000 API incidents across thousands of environments, while measurements show that API traffic dominates overall web traffic. The estimated annual economic impact from vulnerable APIs and automated abuse runs into the tens of billions^[ref].

🚨 How to make your APIs boring to attack (practical, low-friction steps)

Live inventory - maintain a single, up-to-date catalog of every API, version, and owner; promptly decommission unused endpoints to prevent "zombie API" vulnerabilities.

Enforce object-level checks - verify on every read/write that a caller is allowed to access that specific object (deny-by-default).

Token hygiene - use short-lived tokens, rotate keys, require stronger client identity for sensitive calls, and log token use for anomalies.

Behavior-based bot controls - per-endpoint rate limits, anomaly detection tuned for API patterns, and step-up verification only where needed.

Business-logic testing - include abuse-case tests in QA and red-team exercises (coupons, referrals, gift-cards, refunds).

Third-party vigilance - treat partner/third-party APIs as part of your attack surface: monitor, limit privileges, and require security SLAs. Organizations now use 131 third-party APIs on average, but only 16% can effectively mitigate external API risks.

Detect & block zombies - run regular scans for undocumented or deprecated endpoints and apply default-deny rules until explicitly approved.

🔎 Start with an API inventory audit - you can't protect what you don't know exists. Most breaches target shadow APIs that security teams never knew were exposed.