Filter avoidance

"Users may not post from proxies, VPNs, or Tor exit nodes."

- 4chan, rule number 14

Filter avoidance is the unethical practice of using web proxies or VPNs to evade spam detection and IP bans. The user connects to a proxy server, which is often through a webhost, and browses the internet from the proxy server. From the webhost administrator, the only thing they can see is the webhost/proxy server IP and is unable to trace it back to the actual user. Some websites such as Wikipedia detect and block proxies by testing if the IP address accepts a connection through a certain port.

Ban evasion
As proxies mask the user's IP address, sockpuppets and trolls can use them to evade IP bans. Usually, on IPv6, it is harder to block IPv6 addresses because spoofing the MAC address can also change the IPv6 as each computer gets its own IPv6 address, opposed to an IPv4 address where every computer shares a web IPv4 address. Trolls often times use this alongside 10minutemail to troll sites and create tons of bots using temporary email addresses, though there are reportedly sites trying to crack down on temporary email addresses, like Vyond, and many NSFW sites like 4chan already block the use of these.

Similar to ban evasion, VPNs are often used to download torrents of pirated content. Internet service providers detect users downloading known piracy torrent files to detect piracy, however, using a VPN can mask it.

Examples of countermeasures
Strawpoll, a poll site that is also used by governments/companies. They strictly block the use of VPN voting via IP address blacklisting & proxy server detection (if the IP address/port accepts the connection through it and lets it connect to other sites from that IP address) as well as blocking 10minutemail addresses via a blacklist.

On Wikipedia, 90 percent of all IP address/anonymous blocks are "blocked proxy", which are now busted by a bot that tests the IP address's connectivity.

While some Discord servers allow unlogged users, Discord may require logging in or even phone verification if the user is coming from a proxy or known suspicious IP. Some servers can set their security level to require phone verification, which requires verifying a real cell phone number (most VOIP numbers won't work); however, this will also prevent users who don't have a cell phone or a compatible phone number from joining.

Many websites also blacklist disposable email addresses such as those from 10minutemail, Fake Mail Generator, Guerrilla Mail, etc.

Non-malicious uses of proxies
Proxies may also be used for circumventing restrictions from web filters, typically on school or work networks. They may also be used for privacy on monitored networks. Many proxies are blocked on such networks, however, some use a non-static domain or IP address, which means even if that domain is manually blacklisted, it unblocks itself by changing the URL or IP regularly. In China, VPNs are often used to bypass the Great Firewall, however, it is illegal and people who are caught may face legal trouble.

As public proxy servers exist in many countries, proxies can be used to access a website from another country's IP address to view region-restricted content. For example, some content is published on Netflix only in certain countries; however, Netflix has been cracking down on this practice by blacklisting the IP addresses of popular proxy servers.

An increasing use of proxies or proxy extensions is to view certain sites that use a "free article limit" daily system that is designed not through the site's cookies, but is rather bound to IP addresses, such as Bloomberg and New York Times for example. Via using a different IP address, each IP address would get its own limit and if that "free article limit" were to be used up for that one IP address, one could simply switch to another one.

Examples of proxies

 * There are PHP/Glype-dedicated proxy sites, such as ProxySite and others. Often times, they function as a "site-within-a-site", and sometimes load the site very poorly to be not as usable as a "personal VPN", such as NordVPN.
 * The defunct stream-sharing site Rabb.it had a pop-up browser which had a proxy, which was best known when QuackityHQ used it for his raids to bypass IP bans whenever they were enforced on him during livestreams.
 * Firefox was the only browser to have integrated proxy settings, which caused the trend of proxy server lists. Not only are these notoriously loaded by spambots who spider the site and take advantage of them, they are often times much slower.
 * You can get a proxy switcher off of the Chrome web store, and VPN extensions which tend to be less loaded with spambots.
 * Epic Browser's integrated proxy is a major example, being that it gives eight different regions and changing IPs.
 * Similarly, Brave integrates Tor as an option and Opera has a slower but ineffective VPN. It should be noted that these will easily trigger "ipv4.google" errors, as they're often times loaded by spambots.