Lately, using proxies to ensure privacy, digital marketing, or analytics has become a necessity. You’ve purchased a high-quality proxy, set up a profile in a specialized browser, and prepared cookies for a stable session. But shortly after logging into a platform's advertising account, access may be restricted. The reason? “Suspicious network activity.”

According to recent Imperva Bad Bot Reports, over 70% of restrictions on advertising platforms are related to network inconsistencies, not just behavioral factors. The security systems of major IT corporations have evolved: they don't just check the IP against reputation databases, but analyze the integrity and “physics” of the connection using machine learning. A proxy server, as an intermediate node, must be configured correctly to avoid raising suspicion.

In this article, we will look at 7 levels of verification that platforms analyze to assess connection quality. We will break down technical details, examples, and correct configuration methods. For clarity, we use tools like Wireshark, browserleaks.com, and the IP checker from CyberYozh App (links at the end of the article).

Level 1: ASN and Connection Type

This is a basic parameter critical for connection trust. Every IP address has a “passport” — its affiliation with an Autonomous System (ASN), which can be checked via WHOIS or databases like MaxMind.

ASN Types:

ISP: Home internet (Comcast, Verizon, Lietpark Communications).
Mobile: Mobile operators (T-Mobile, THREE, Vodafone).
Hosting/Business: Data centers (AWS, DigitalOcean, Hetzner).

Nuance: Standard server proxies are hosted in data centers where their ASN is labeled as “Business.” Additionally, reverse DNS (rDNS) often reveals a technical domain: instead of user.provider.com — server.example.com.

Example: A user authenticates in a service with a “Chrome / Windows 10” User-Agent, but the traffic comes from a data center in Frankfurt, which is uncharacteristic for a home user.
Conclusion: The system classifies the connection as technical or a VPN. The Trust Score decreases.
Solution: For tasks requiring a high level of trust, choose residential or mobile proxies with ASNs from real providers. Check rDNS for compliance with provider standards.

Level 2: Passive OS Fingerprinting (p0f and TCP/IP Stack)

This involves deep analysis: checking the TCP/IP stack. Operating systems form network packets in unique ways. Tools like p0f allow for the passive determination of the source traffic's OS.

Key Parameters:

TTL (Time To Live): Windows — 128, Linux/Android/iOS — 64.
Window Size: The size of the receive window.
TCP Options: Header order (e.g., MSS, Timestamp).
TLS Fingerprinting (JA3): The system analyzes the structure of the TLS Client Hello.
- Clarification: When using HTTP/SOCKS proxies (CONNECT method), the TLS handshake comes from the client. JA3 in this case helps identify software mismatches with the declared User-Agent. However, if the proxy interferes with traffic or is not configured for clean tunneling, it can distort fingerprints. The use of a Linux server as a gateway is often identified precisely through TCP/IP fingerprinting (TTL).
Example: “Windows 10” is selected in the profile settings, but the connection goes through a proxy server on Ubuntu (Linux). The system sees a Windows User-Agent, but incoming TCP packets have a TTL of 64 (characteristic of Linux), not 128.
Conclusion: Mismatch. The system determines that traffic is passing through an intermediate node. This can lower trust.
Solution: Modern privacy browsers work correctly with JA3, but it's important to consider the server settings themselves.
1. Synchronization: Ideally, the proxy OS should match the profile (e.g., Android mobile proxies for an Android profile).
2. Passive OS Fingerprinting: Use providers (such as CyberYozh App) that support TCP/IP stack synchronization at the network level. This allows the proxy to send packets that technically match the OS declared in the profile (Windows or macOS).

Level 3: MTU and MSS — Packet Settings

MTU (Maximum Transmission Unit) — the maximum packet size without fragmentation. MSS (Maximum Segment Size) — the payload capacity of the packet.

Standards:

Ethernet (standard): 1500
Mobile Networks (4G/5G): 1420–1480

If a proxy is used but the MTU is characteristic of tunneling (e.g., 1300), this may indicate the use of VPN protocols (OpenVPN, WireGuard) instead of a direct connection.

Example: The IP is identified as residential, but an MTU of 1300 is a sign of a tunnel. This is also noticeable in the QUIC protocol (UDP).
Conclusion: Technical connection parameters differ from standard ones.
Solution: Check MTU via browserleaks.com or network analyzers. Configure the connection so that values match the standards of the emulated network.

Level 4: Latency and Geolocation

Security systems use timing analysis: RTT (Round Trip Time) is compared with the declared geolocation.

Scenario: The proxy is located in New York, while the user is in a different region.

Route: User location → New York → Target server.
The RTT might be 300 ms, whereas for a local user in New York, the norm is 20–30 ms.

Addition: Verification via CDN is possible — measuring response times from different servers to triangulate the location.

Example: IP is identified as USA, but the signal delay corresponds to another continent.
Conclusion: Mismatch between geolocation and network response.
Solution: Choose proxies with minimal ping. Avoid unnecessary routing nodes. Ensure that browser geolocation settings do not conflict with the IP.

Level 5: Open Ports and Configuration

Incorrectly configured proxies may leave service ports open for external scanning. Additionally, WebRTC scripts can reveal the local IP address.

What systems look for:

Open ports 3128, 8080, 1080 (standard for proxies).
Remote access ports: 22 (SSH), 23 (Telnet), 3389 (RDP).
WebRTC: Leaks of the real local IP through the browser.

For regular users, these ports are typically closed by NAT.

Example: Scanning shows the presence of open server management ports.
Conclusion: The device is identified as a server, not a user terminal.
Solution: Use services with incoming port filtering. Correctly configure WebRTC (or disable it) to prevent data leaks.

Level 6: Browser Profiles and Behavior

Proxy quality must be backed by correct browser configuration. Systems analyze the consistency of network data and software parameters.

Important Points:

Timezone & Language: If the IP is in London, but the browser time is UTC+3, it's a clear mismatch.
Hardware: User-Agent claims a mobile device, but network metrics (MTU, Latency) are characteristic of a wired data center internet.
Behavior: Overly linear cursor movements, absence of natural delays, or “Impossible Travel” (changing countries in an unrealistic timeframe).
Example: The system detects automated behavioral patterns despite a high-quality IP.
Conclusion: Complex anomaly in the profile.
Solution: Use professional tools for profile management. Synchronize time zone and locale with IP data. Adhere to natural navigation scenarios.

Level 7: IP History and Reputation

Security systems rely on the address's activity history. Databases (IPQS, MaxMind, etc.) assign risk scores to IPs based on previously recorded incidents.

Example: The IP address is technically clean now, but was previously used for spamming and is in a reputation database with a high Risk Score.
Conclusion: Low address reputation can lead to preemptive restrictions.
Solution: Don't rely solely on simple free checkers. Use professional aggregators like the CyberYozh App IP Checker. We use data from premium databases (including IPQS and MaxMind) to show a real trust assessment of the address.

💡 How to read the report? To correctly interpret Fraud Score parameters and evaluate connection quality, we recommend studying our detailed guide on working with the checker.

Connection Myths in 2025

❌ Myth 1: VPN is more reliable than proxy. Reality: VPNs often add redundant service data and are easier for services to detect due to encryption specifics.

❌ Myth 2: Free proxies are suitable for work. Reality: Such addresses often have poor reputations, slow speeds, and are insecure.

❌ Myth 3: Only the IP matters. Reality: The full technology stack is analyzed — from TCP packets to browser settings.

Conclusion: How to Ensure a Stable Connection?

Traffic analysis systems are attentive to details. In 2025, using a proxy is a matter of competent infrastructure and configuration.

Your Checklist:

ASN and IP: Priority to residential/mobile addresses. Check rDNS correctness.
Fingerprints: Synchronize TCP/IP (Passive OS Fingerprinting) and TLS (JA3).
Protocol: Use SOCKS5 for data transmission purity.
Latency/MTU: Minimize delays, check MTU for compliance with standards.
Ports/WebRTC: Ensure unnecessary ports are closed and the local IP doesn't leak.
Behavior: Act like a regular user.
Verification: Use CyberYozh App IP Checker to analyze IP reputation and browserleaks.com to check browser settings.

In the CyberYozh App catalog, we consider these parameters at the architectural level. We provide high-quality IPs with Passive OS Fingerprinting support (check availability with support), so you can focus on work tasks without technical failures.

Sources and Tools:

Digital proxy footprints: How do Facebook/Google actually determine that you are using a proxy?