PaloAlto Networks

https://urlfiltering.paloaltonetworks.com/

Fortinet

http://metal.fortiguard.com/tests/

MxToolbox

https://mxtoolbox.com/

IANA

https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml

Microsoft

https://testconnectivity.microsoft.com/

Qualys

https://www.ssllabs.com/ssltest/

Bad SSL

https://badssl.com/

McAfee

https://www.trustedsource.org/

Google

https://transparencyreport.google.com/

Heise

https://www.heise.de/tools/

Jodies

http://jodies.de/ipcalc

Huawei Marine

https://www.submarinecablemap.com/

RIPE NCC

https://stat.ripe.net/

Common Vulnerabilities and Exposures

https://cve.mitre.org/cve/search_cve_list.html

https://www.cvedetails.com/

Virustotal

https://www.virustotal.com/de/

Lorem Ipsum

http://www.loremipsum.de/