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If DNS resolution is disrupted but the site is not blocked in other ways, it may be possible to access a site directly through its IP address or modifying the host file. Using alternative DNS servers, or public recursive name servers (especially when used through an encrypted DNS client), may bypass DNS-based blocking. [1]
DNS hijacking, DNS poisoning, or DNS redirection is the practice of subverting the resolution of Domain Name System (DNS) queries. [1] This can be achieved by malware that overrides a computer's TCP/IP configuration to point at a rogue DNS server under the control of an attacker, or through modifying the behaviour of a trusted DNS server so that it does not comply with internet standards.
A typical circumvention method is to find an alternative DNS resolver that resolves domain names correctly, but domain name servers are subject to blockage as well, especially IP address blocking. Another workaround is to bypass DNS if the IP address is obtainable from other sources and is not itself blocked.
A DNS sinkhole, also known as a sinkhole server, Internet sinkhole, or Blackhole DNS [1] is a Domain Name System (DNS) server that has been configured to hand out non-routable addresses for a certain set of domain names. Computers that use the sinkhole fail to access the real site. [2]
The latter case where the user is redirected to another destination would be considered DNS Spoofing, otherwise known as "DNS Poisoning". [3] DNS blocking can be applied to individual servers/IP address, or entire blocks of IP addresses for multiple reasons. Some public DNS Resolvers, like Quad9 and CleanBrowsing, offer filters as part of their ...
The IP address of a public server is also important, similar in global uniqueness to a postal address or telephone number. Both IP address and port number must be correctly known by all hosts wishing to successfully communicate. Private IP addresses as described in RFC 1918 are usable only on private networks not directly connected to the internet.
DNS servers in the chain can filter out private IP addresses and loopback IP addresses: External public DNS servers (e.g. OpenDNS) can implement DNS filtering. [5] Local system administrators can configure the organization's local nameserver(s) to block the resolution of external names into internal IP addresses. (This has the downside of ...
Reverse DNS queries are used to map IP addresses to domain names. They are PTR queries for subdomains of in-addr.arpa (for IPv4 addresses) [ 3 ] and ip6.arpa (for IPv6 addresses). [ 4 ] For example, to find the domain name associated with the IP address 203.0.113.22, one would send a PTR query for 22.133.0.203.in-addr.arpa .