I try to figure out which IP is a residential proxy. The most IP's with a fraud score +75 has an open port 25.

A normal visitor's IP does not have port 25 open.

So you can assume that it is a configured IP address, right.

My questions

  1. Is there a relatively reliable way to expose a residential proxy IP if that IP is using/opening port 25?

  2. Is it possible to query an IP that calls a webstei directly on an open port 25 and then block it accordingly. ....IF ip-port_25=true THAN add_to_htaccess_blacklist; ?

  • u can use a database on httaccess or u block the ip direct over iptables. Do u need the check direct, or do u have some kind of time? for the last i would check the access log over cronjob and try making a connection over telnet/php later u can easy rewrite the httacces with. When u want direct response i would make fake image going to a php file who did the check for u
    – StefanBD
    Nov 27, 2022 at 22:35
  • 1
    You mean I should not be able to browse your website if I accept mail on the same IP? What kind of website has that requirement?
    – anx
    Nov 27, 2022 at 23:21
  • Hi StefanBD, thank you for your answer. I really appreciate it. Your ideas - both - are fine! I like them. So, I need to write a bash script to do the logfile job. Yes, that's it! Then, the check via a fake image sounds interesting. Do you have some details about how it should work?
    – Legion
    Nov 27, 2022 at 23:25
  • @anx - About your first question: Yep, you are a not wished visitor in that case (bye bye baby). Ok, let's be serious: My customer works in the valuable metals sector and is currently having massive problems with IP addresses, which on the one hand scrape certain content. 24/7 long. He doesn't want that. I can certainly understand why you don't want that in certain areas. Even if it's difficult to prevent. On the other hand (his main problem): fake orders are placed daily (for whatever reason) via residential proxies (G3/G4 mobile proxies).Hosting IP's can be blocked from 0 to 100 in seconds
    – Legion
    Nov 27, 2022 at 23:35
  • U can generate images or output images with php so u can do with mode rewrite image.png goes to tool.php who does the check like connect to the visitor ip(u got from request variable) and if a login to the mailserver is possible u add the ip to the httaccess and give out a image with header png and code of 1 pixel, this method is used in tracking pixels for example
    – StefanBD
    Nov 27, 2022 at 23:41


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