I have nothing against proxies. They have many legitimate uses. But I run a website too, and part of managing the community means dealing with members who evade bans or obscure their identity through the malicious use of proxies. I was frustrated that there is no reliable way to detect if someone is using a proxy based on their IP, so I came up with my own solution, the Black Box Proxy Block.
The goal is to detect all open HTTP, SOCKS, and web-based proxies, Tor exit nodes, dedicated servers, and public VPNs. Of course that's not really obtainable, but I'm getting closer all the time. When I discover a proxy that was missed I try to figure out how to automate its detection in the future, and some of our members seem very determined to help with the process. :) After nearly a decade in service on a site with 1 million+ unique visitors a month, it has become fairly reliable.
To test the Black Box Proxy Block, just enter an IP address here:
Integrating the service into your own site is easy. When you want to check if someone is using a proxy, simply request:http://www.shroomery.org/ythan/
The response is a single character and will contain one of three values: Y if it's a proxy, N if it isn't, or X if there's an error.
This service only detects open proxies and dedicated servers. You may also want to consider using Stop Forum Spam and BotScout to check for known bots and spammers.
If you have any feedback, questions, suggestions, or want to report false positives or false negatives, please contact me.
Frequently Asked Questions:
Q: Can I have a copy of your database, or run the script locally?
A: Honestly I'd really rather not share it. That's where the "black box" part of the name comes from. ;) This is first and foremost a service for my own use. The public interface was just an afterthought. If you can benefit from it too, awesome! I plan to keep it online and freely available for the foreseeable future. But I don't want to compromise its effectiveness by giving away details about how it works. I believe security through obscurity has its place, and I'd rather not offer proxy admins any advantages when it comes to preventing detection. However, if your use case requires offline screening and you don't mind paying a modest subscription fee, please see the question at the bottom about our business-class service. I've attempted to make it easily affordable for any legitimate company, while keeping the price high enough to dissuade malicious individuals from abusing the data.
Q: Can you help me integrate proxy blocking into my site?
A: If you want to hire me as an independent contractor, sure! Drop me an e-mail and we can discuss specifics. Otherwise, I'd recommend posting on the official message board for the software you're running, and see if someone with experience can help you. Most complex scripts already have methods in place for retrieving remote files and caching results, so it shouldn't be too difficult for someone who's familiar with the code.
Q: Do you have any plans to offer this service in the form of a DNSBL?
A: I'd love to. I understand it would be more convenient in a lot of situations. I tried to set it up once, but ended up breaking BIND. Unfortunately I don't have lots of free time to spend on this project, but if anyone has experience running an RBL and wants to help me out, please get in touch.
Q: Are there any other similar services out there?
A: Yes, although I've found them to be deficient in one way or another for my own personal needs. But you may wish to check out BlockScript, MaxMind, ThreatMetrix, FireHOL, IP Intelligence, Proxycheck.io, BadIPs, or Nasty Hosts. There are also some relevant DNSBLs like proxies.dnsbl.sorbs.net and bl.blocklist.de.
Q: Is there a limit to how much I can use this service?
A: No, there's no limit, although when you check an IP I'd appreciate it if you cache the result to eliminate redundant requests. However, please make sure your own code fails gracefully if it receives unexpected input, or if the proxy check times out. This site uses Cloudflare, so if you somehow trigger their DoS protection, you'll be presented with a CAPTCHA instead of the results you were expecting. Also, sometimes we just experience good old-fashioned downtime. Make sure you plan accordingly, so if I screw up, it doesn't break your site. ;)
Q: Is this service still maintained?
A: Yes, and actively so! Although this landing page isn't updated frequently, I'm adding new IPs every day through manual and automatic detection. This service has been online for almost a decade and I rely on it for my own projects, so it's not going anywhere. If circumstances change, this answer will be updated.
Q: Is there a business-class version of this service?
A: There is! If you wish to perform offline screening, fraud detection, or analytics, you can subscribe for $100/month. As long as your subscription is active, you can download a current copy of our proxy IP list whenever you want and use it for all internal purposes. Please contact us for more information, or check out the subscription agreement for additional details.