Five years ago, blocking fraud was simple: block AWS IP ranges, block known VPN exit nodes, done. Today that approach catches less than 30% of sophisticated fraud attempts.
The shift happened gradually, then all at once. Underground proxy marketplaces realized that residential IPs were worth far more than datacenter IPs because no blocklist would ever touch them.
How Residential Proxies Are Harvested
Free VPN apps, browser extensions that promise "free unlimited bandwidth," and pirated software installers all contain silent SDKs that enroll the victim's device as a proxy exit node. The victim has no idea. Their IP looks completely clean to any fraud API that checks it.
Why IP Reputation Fails Here
These IPs are genuinely clean. They've never sent spam. They've never been on an abuse list. Sentinel defeats residential proxy evasion by looking past the IP entirely — analyzing the TCP/IP stack fingerprint, MTU packet size anomalies, and cross-network velocity patterns.