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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]
Instead of returning the valid IP address of a requested site (for example, instead of 198.35.26.96 being returned by the DNS when "www.wikipedia.org" is entered into a browser, [2] if this IP were on a block list, the DNS might reply that the domain is unknown or with a different IP address that directs to a site with a page stating that the ...
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 .
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 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]
Unix-like operating systems commonly implement IP address blocking using a TCP wrapper, configured by host access control files /etc/hosts.deny and /etc/hosts.allow.. Both companies and schools offering remote user access use Linux programs such as DenyHosts or Fail2ban for protection from unauthorized access while allowing permitted remote access.
A wildcard DNS record is a record in a DNS zone that will match requests for non-existent domain names. A wildcard DNS record is specified by using a * as the leftmost label (part) of a domain name, e.g. *.example.com. The exact rules for when a wildcard will match are specified in RFC 1034, but the rules are neither intuitive nor clearly ...