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README.md

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 # bad-asn-list
 An open source list of ASNs known to belong to cloud, managed hosting, and colo facilities.
+
+## The Problem
+
+This list came after spending far too long searching for a good way to keep automated bots, spammers, and scammers off the social network I created, Nearby. I found that after we hit a certain size (around 500K monthly active users), the flood of these bad actors became entirely unmanagable. I tried countless detection methods, but most of them resulted in too many missed and/or false positives. 
+
+I tried offloading the account creation process to depend on the user having a Facebook profile, thinking that would solve the problem. It didn't help at all. Next I tried Google sign-in, but it also was entirely ineffective. I eventually tried to outsource the problem to a company called MaxMind. Their API actually worked very well, but it was prohibitively expensive for our purposes. 
+
+## The Solution
+
+I continued to deepen my understanding of the bad traffic and I eventually realized that almost all the bad traffic was coming from hosting/colo facilities and cloud service providers. Even traffic coming from VPNs was originating from a hosting facility where the VPN provider was located. I built a list of ASNs which belong to known hosting/colo/cloud providers. Whenever a new account was being created, I looked-up the ASN that owns the IP address. I then checked if that ASN was included in the list I had created and if so, prevented the account from being created.
+
+You might think that this would block a lot of good traffic, but from all of my tests, that doesn't appear to be the case at all. Furthermore, the problem was about 90% solved.  Almost all the bad traffic vanished.
+
+I've been testing out this solution for a few months now and it's been going amazingly well. I know that I am not the only person who has faced this problem, so I decided to open-source my list. Feel free to submit pull requests if you have any updates to the list you'd like to share.
+
+## Implementation
+
+1. Load this list into a database or in-memory.
+2. When a request comes in, determine the ASN for the request's ip address. There are a number of ways to do this. For example, MaxMind offers a free database that maps IP address to ASN: http://dev.maxmind.com/geoip/geoip2/geolite2/
+3. Check if the IP address' ASN is included in the list from step 1.  If so, block the request, increase fraud score, etc.
+
+Hopefully this will help save someone from wasting as many hours I have trying to solve this problem!
+
+Brian Hamachek ([email protected])