Free Proxies Steal Passwords and Card Data: How to Check Security Before Use

You found a free proxy, connected it — and it works. But while you rejoice at the "freebie," the operator of this proxy can read everything you enter: usernames, passwords, card numbers, session tokens from advertising accounts. This is not a theory — it is a documented scheme for profiting from free proxy services.

In this article, we will explore how data theft through proxies works, how to check any proxy before use, and why arbitrage specialists, SMM professionals, and marketplace sellers are particularly vulnerable.

How Free Proxy Services Actually Make Money

The first question that should arise for any sane person is: why would someone maintain a proxy server for free? Servers cost money. Traffic costs money. Support costs money. If you are not paying with cash — you are paying with something else.

Here are the real business models of free proxies that no one will tell you about on a site with a nice interface:

Model 1: Intercepting and Selling Traffic

The proxy server operator sees all your HTTP traffic in plain text. If the site you are visiting uses an unprotected connection — the login and password are transmitted as plain text. The operator collects this data and sells account databases on closed forums. A database with 10,000 Facebook accounts can sell for between $200 and $2000 — depending on the "quality" of the accounts.

Model 2: SSL Stripping and HTTPS Attacks

Many think: "I have HTTPS, so everything is encrypted, the proxy sees nothing." This is a dangerous misconception. There is an SSL stripping attack: the proxy intercepts your request before establishing a secure connection and replaces HTTPS with HTTP. The browser shows an unprotected connection, but most users do not pay attention to this. As a result, all traffic, including passwords and card data, goes in plain text through the attacker’s server.

Model 3: Certificate Spoofing (Man-in-the-Middle)

A more advanced scheme involves installing a custom root certificate on the user's device. After that, the proxy can decrypt HTTPS traffic, read its content, and re-encrypt it before sending it to the destination server. The user sees a green lock in the browser and suspects nothing. This is how some corporate proxies work (this is legal within the company), but fraudulent services can operate in exactly the same way.

Model 4: Using Your IP as an Exit Node

Some "free" VPN and proxy applications use their users' devices as proxy servers for other clients. This means that through your internet connection and your IP address, someone else is doing whatever they want — scraping, spamming, inflating numbers, or in the worst case — illegal operations. The responsibility formally falls on your IP.

What Exactly is Stolen Through Free Proxies

Let's be specific — what exactly is at risk when you use an unverified free proxy in your work:

It is also worth mentioning content modification of pages. Some free proxies inject third-party scripts into the HTML code of visited sites — ads, cryptocurrency miners, phishing forms. You visit a legitimate site, but see its altered version with foreign content. In the context of working with advertising accounts, this is particularly dangerous: a modified card input form looks like the real one.

Who is at Risk: Arbitrage, SMM, E-commerce

If you are reading this article, you are likely working with multiple accounts and advertising accounts. Such users are the most attractive targets for operators of fraudulent proxies. Here’s why:

Arbitrage Specialists and Media Buyers

An arbitrage specialist works with Facebook Ads, TikTok Ads, Google Ads. At one workstation, 5-20 advertising accounts can be open simultaneously. Each account is linked to a card with real money. If the proxy intercepts the session token of at least one account — the attacker gains access to manage advertising and linked payment methods. The budget can be drained in a matter of hours before you even notice.

Anti-detect browsers are used to work with advertising accounts — Dolphin Anty, AdsPower, GoLogin, Multilogin. If the proxy is set up inside the anti-detect browser and it is compromised, the attacker sees all traffic from all profiles at once.

SMM Specialists and Agencies

An SMM specialist manages clients' accounts on Instagram, TikTok, VK. Using a free proxy means that the login data for clients' accounts passes through someone else's server. Hacking a client account is not only a loss of income but also reputational damage, complaints, and potential lawsuits. Restoring client trust after such an incident is extremely difficult.

Marketplace Sellers

Sellers on Wildberries, Ozon, Avito use proxies to monitor competitors' prices and manage multiple stores. A seller's personal account on Wildberries provides access to inventory, prices, financial statistics, and payouts. Compromising this data can lead to unauthorized price changes, fund withdrawals, or store blocking.

How to Check Proxy Safety: Step-by-Step Checklist

If you still decide to use an unfamiliar proxy or want to check one you are already using — here is a sequence of actions. None of these steps require programming knowledge.

Step 1: Check the Proxy's IP Address and Geolocation

Connect to the proxy and visit 2ip.ru or whoer.net. The site will show your current IP address. Check:

• The IP address has changed to the proxy's address (meaning traffic is indeed going through the proxy)
• The country and city match those stated on the proxy provider's site
• No labels "Proxy," "VPN," "Datacenter" in the anonymity section — if they exist, the proxy is easily identifiable by platforms

Step 2: Check for DNS Leaks

A DNS leak occurs when your browser uses the proxy to transmit data, but DNS requests (i.e., requests to resolve website addresses) still go through your real internet provider. This reveals your real IP and location.

Check:

1. Connect to the proxy
2. Visit dnsleaktest.com
3. Click "Standard test" or "Extended test"
4. Results should only show DNS servers belonging to the proxy provider — not your home provider

Step 3: Check SSL Certificate Authenticity

This is the most important check for protecting passwords and card data. The algorithm:

1. Connect to the proxy
2. Visit any major site: google.com, facebook.com, vk.com
3. Click on the lock icon in the browser's address bar → "Certificate" (or "Site Information")
4. Check the "Issued by" field: the certificate should be issued by a well-known certification authority — Let's Encrypt, DigiCert, GlobalSign, Comodo
5. Red Flag: if the certificate is issued by an unknown organization or the site itself — this is a sign of a MitM attack

Step 4: Check for HTML Code Modification of Pages

Access any well-known site through the proxy and open the page source (Ctrl+U in Chrome/Firefox). Look for suspicious inserts:

• Unknown <script> tags at the beginning or end of the page
• Links to unknown domains in scripts
• Iframe inserts that should not be on the page
• Modified input forms (the action attribute of the form leads to a non-original domain)

For comparison, you can open the same page without the proxy and compare the source code — the differences will be immediately apparent.

Step 5: Check the Reputation of the Proxy's IP Address

Connect to the proxy, find its IP through 2ip.ru, and check this IP in the following services:

• abuseipdb.com — database of complaints about IP addresses (spam, attacks, fraud)
• scamalytics.com — risk assessment of the IP address
• ipqualityscore.com — check for belonging to proxies, VPNs, botnets

If the IP is marked as "High Risk," "Proxy," "VPN," or has complaints — this is a bad sign for both safety and use in working with advertising platforms.

Red Flags: Signs of a Dangerous Proxy

Sometimes you don’t even need to run checks — a dangerous proxy can be recognized at the selection stage. Here are the signs that should raise your alarm:

A separate note about browser extensions. Many free "proxies" are distributed specifically as extensions for Chrome or Firefox. A browser extension has access to everything you do in the browser: page content, entered data, cookies, history. This is a fundamentally different level of access compared to a regular proxy server. Never install extensions from unknown developers for working with advertising accounts and client accounts.

Tools for Checking Proxies (No Code Required)

We have compiled all useful services into one table — for convenience, bookmark it:

Pay special attention to WebRTC leaks. WebRTC is a browser technology for video calls and data transfer. The problem is that the browser can reveal your real IP address through WebRTC even when a proxy is active. This is one of the most common reasons why Facebook and other platforms "see" your real address despite the proxy. You can check this on browserleaks.com in the WebRTC Leak Test section.

Safe Alternatives: What to Use Instead of Free Proxies

After all the above, a logical question arises: what to use instead of free proxies? The answer depends on the task.

For Arbitrage Specialists: Mobile Proxies

Arbitrage specialists working with Facebook Ads and TikTok Ads traditionally choose mobile proxies — they use IP addresses from real mobile devices in operator networks (MTS, Beeline, T-Mobile, etc.). Facebook and TikTok algorithms see such traffic as coming from a regular user with a smartphone, which significantly reduces the likelihood of blocking. The key advantage is a high level of trust from advertising platforms.

For SMM Specialists: Residential Proxies

SMM agencies managing 10-50 client accounts on Instagram and TikTok will benefit from residential proxies. They operate through the IP addresses of home internet users — this is how a "normal" user appears to social media algorithms. Residential proxies ensure stable operation when managing multiple accounts without the risk of mass bans.

For Price Monitoring and Scraping: Datacenter Proxies

If your task is to scrape prices on Wildberries, Ozon, or Avito, rather than work with accounts, then datacenter proxies will be the optimal choice. They are faster than residential ones, cheaper, and handle tasks where a high level of "humanity" in traffic is not required. For price monitoring, speed is more important than anonymity — and here datacenters win.

Key Criteria for Choosing a Safe Paid Proxy

• Legal Entity and Public Privacy Policy — the provider is responsible for your data
• No-Log Policy — the provider does not store logs of your activity
• Traffic Encryption — data between you and the proxy server is encrypted
• Technical Support — there is someone to contact in case of problems
• Reviews on Independent Platforms — Trustpilot, specialized forums for arbitrage specialists
• Trial Period or Test Rate — the opportunity to test quality before full payment

Conclusion

A free proxy is not just a slow or unreliable tool. In the worst case, it is an active threat to your money, accounts, and reputation with clients. Operators of free proxies profit from intercepting traffic, selling data, and using your device for their purposes. This is not paranoia — it is a documented reality confirmed by independent research.

If you are already using a free proxy in your work — right now, check it through whoer.net and dnsleaktest.com. If the results raise concerns — change the tool before you lose access to advertising accounts or client accounts.

For professional work with multiple accounts on Instagram and TikTok, with Facebook Ads advertising accounts, or for monitoring marketplaces — we recommend considering residential proxies: they provide a real level of anonymity, do not end up on platform blacklists, and operate on a predictable, controlled infrastructure. Your data remains yours.