Why can't I access the Skype website (error NET::ERR_CERT_AUTHORITY_INVALID)?

Whether I use Firefox or Chrome, I'm not able to access the website. I get the following on Chrome:

Your connection is not private Attackers might be trying to steal your information from (for example, passwords, messages, or credit cards). Learn more NET::ERR_CERT_AUTHORITY_INVALID Subject:

Issuer: Cisco Umbrella Secondary SubCA fra-SG

Expires on: Feb 22, 2022

Current date: Feb 19, 2022

And on Firefox:

Warning: Potential Security Risk Ahead

Firefox detected a potential security threat and did not continue to . If you visit this site, attackers could try to steal information like your passwords, emails, or credit card details.

What can you do about it?

The issue is most likely with the web site, and there is nothing you can do to resolve it.

If you are on a corporate network or using anti-virus software, you can reach out to the support teams for assistance. You can also notify the web site’s administrator about the problem.

I am on Ubuntu 21:10, fully updated (just completed sudo apt update/upgrade, which I do every day or so) and restarted my PC. I've also noticed for that the last few days that I can't access , getting the same security warnings.

1 Answer

This is probably related with your DNS server. Are you in a corporate environment? Maybe those sites are being filtered.

You can get some clues with dig. This is what I see on my machine:

$ dig skype.com
; <<>> DiG 9.10.3-P4-Ubuntu <<>> skype.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26835
;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;skype.com. IN A
;; ANSWER SECTION:
skype.com. 240 IN A 40.76.4.15
skype.com. 240 IN A 40.112.72.205
skype.com. 240 IN A 40.113.200.201
skype.com. 240 IN A 104.215.148.63
skype.com. 240 IN A 13.77.161.179
;; Query time: 33 msec
;; SERVER: 208.67.222.222#53(208.67.222.222)
;; WHEN: Sat Feb 19 11:07:36 -03 2022
;; MSG SIZE rcvd: 118

Compare the answer section, then check if the IP's you are getting match with those legitimate owned by skype (i.e. check with some whois online tool). Of course I'm only guessing; it may be another completely different problem; dig is only one tool, but usually can help to point out in the right direction.