Can Cisco Umbrella security block site access due to Cloudflare DNS

A customer of ours using Cisco Umbrella security is being blocked from accessing our site. Some suggest it is because DNS is hosted at Cloudflare. Could that really be the case!? Has anyone seen something similar?

Thank you!


Without the exact error message it is impossible to say what the case is.

This is what they get:


Alright, that is a message directly from their security appliance. Only Cisco or the responsible network administrator can shed more light here. DNS should be unrelated, but of course there is the general possibility they take arbitrary parameters such as DNS to impose a block.

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Thank you Sandro. The suggestion I saw from someone when researching it was that Cloudflare DNS hosted sites was viewed as a potential security threat, because some malicious sites are using Cloudflare. Hopefully that is untrue.

I dont think this will be the case, but in theory - respectively technically - it is possible they block everything that is remotely related to Cloudflare.

Hi Lauridsen,

I was blocked some weeks ago in public library, similar situation as you describe and at that time found these two articles that iā€™m recommending to you, basically your customer IT team should follow these steps:

First they can try to figure the category your website block falls under:
# How to Read the Diagnostic Information on Block Pages

Then they should report your domain as false positive:
# How to Request a Security Reclassification for a Domain


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