topic Re: URL Filtering: Can't Block website when user use Google Cache in General Topics

URL Filtering: Can't Block website when user use Google Cache

Vuqar.Musazada — Fri, 23 Sep 2022 05:33:55 GMT

Hello, all

I want to block a website whe user user google cache or yotube,facebook.

In the past i tested everything ok, Palo Alto could block when user use google cach or youtube.

But today, Palo Alto can't block website when user use google cache ( But can block youtube,facebook )

Pls help me know why!!

Palo Alto Block website www.youtube.com

Palo ALto Block when user use yotube.comm,facebook.com

BUT Palo Alto Can't Block when user use google cache !!!!!!!!!!!!!!

Thanks

Re: URL Filtering: Can't Block website when user use Google Cache

aleksandar.astardzhiev — Fri, 23 Sep 2022 06:21:08 GMT

Hey @Vuqar.Musazada ,

So think about how URL filtering works - When user web request hit the firewall it will try to inspect the HTTP header to identify the requested URL. If the traffic is encrypted, firewall will use the SNI from TLS negotiation to figure out at least what domain/hostname the user has requested.

Once the URL is extracted firewall will try to categorize it and check if this selected category is allowed in your policy.

With Google cache user doesn't actually make a request for the required page, but instead he goes to webcache.googleusercontent.com. If you don't perform any SSL/TLS decryption firewall will only be able to get the SNI, which will be for the google webcache server, so URL filtering will think that user is going to google and will not have any visibilty what actual page is served from that cache.

In this case you can block any traffic to webcache.googleusercontent.com. This way you will prevent any user to use google cache.

Now the URL for the actual page is still present as URL parameter so it should be possible to block the actual page only if you apply SSL decryption and firewall have visibility over the full user request.

Re: URL Filtering: Can't Block website when user use Google Cache

Vuqar.Musazada — Fri, 23 Sep 2022 07:29:50 GMT

We do as you said but it doesn't work

Re: URL Filtering: Can't Block website when user use Google Cache

Vuqar.Musazada — Fri, 23 Sep 2022 07:51:05 GMT

So we have divided internet users into 3 groups
 1) internet01 -full authorized ones
 2) internet02 - relatively restricted
 3)iternet03 - restricted
 YouTube, Facebook and other sites are blocked for internet03 (url filtering, url catagory, Social Networking, Streaming Media...)
The block we have set works normally, when the notebook is disconnected from the company network and the Internet is shared with the phone, when you open a YouTube video, save the video and return to the office network, the block does not work (google chrome cache (because it remains in the cache memory). Because the session is not updated, the block is not applied to YouTube and other websites we visit

Re: URL Filtering: Can't Block website when user use Google Cache

Waiphyo97 — Mon, 29 May 2023 04:22:00 GMT

Hello,

According to my testing, you also need to block "quic" app too. After then, you can block specific URLs even users are using google cache.