topic Re: Re: Skype false positive in General Topics

Skype false positive

Interface — Thu, 22 Aug 2013 06:44:43 GMT

Hello guys,

About skype: how to know, when users realy use skype and when PA detects only false positive? Because now i have lot of log with "secure.skype.com" URL and PA detects it as skype application.. I would be grateful for an explanation.

Re: Skype false positive

HULK — Thu, 22 Aug 2013 07:31:12 GMT

Hi Ignas,

Users are using any other video/audio calling application into their machine...? Please follow below mentioned documents for more information about SKYPE.

Controlling Skype

Re: Skype IM Problem

Also I would recommend you to open a case with support.

Thanks

Re: Skype false positive

Interface — Thu, 22 Aug 2013 09:07:48 GMT

Skype not installed on users' computers. We checked this. But PA detects skype application. Detailed log shows "secure.skype.com" URL.

Re: Skype false positive

harshanatarajan — Thu, 22 Aug 2013 09:13:36 GMT

Could be a false positive. Is the firewall on the latest dynamic updates ?

Re: Re: Skype false positive

emr_1 — Thu, 22 Aug 2013 09:56:27 GMT

The URL log as below is generated by accessing to secure.skype.com from IE10.

Do you mean you can't figure out this is actual skype session or just https session from browser?

If my understanding is correct, I guess there is no clue to figure out which pattern is it because the session is encrypted by ssl and PaloAlto device could not see the payload.

However, skype client send out skype-probe session, if you can see skype and skype-probe from one source address, you might be able to say that user is using skype client.

Regards

Re: Skype false positive

Interface — Thu, 22 Aug 2013 11:12:43 GMT

Hi emr,

many thanks for your answer. I can't find skype-probe. So no skype client is being used. I think that users are redirected to a "secure.skype.com" page from some other page or something like that, though I can't say exactly. Because when I type in a web browser "secure.skype.com", i'm redirected to "login.skype.com" and PA log shows few records "secure.skype.com", "login.skype.com" and "apps.skypeassets.com". And when I look at users log, I only see "secure.skype.com" records. I'm trying to figure out how this happens.

Re: Re: Skype false positive

emr_1 — Thu, 22 Aug 2013 11:35:34 GMT

If the user is using skype client, you can find skype-probe in traffic log as below:

I can see all URLs you mentioned. (URL category name might be different from you because I'm using PAN-DB instead of BrightCloud)

What is 'users log' you are pointing to?

Do you mean detail log for 'secure.skype.com'?

Re: Skype false positive

Interface — Thu, 22 Aug 2013 12:07:41 GMT

URL log. I use filter: (url contains skype).

Re: Skype false positive

emr_1 — Thu, 22 Aug 2013 12:48:30 GMT

Well, it looks like your PaloAlto device places between client PC and proxy server.

I'm not using proxy. This might causes different result.

Re: Skype false positive

Interface — Thu, 22 Aug 2013 13:31:22 GMT

Maybe. Anyway thank you for help

Re: Skype false positive

Interface — Fri, 23 Aug 2013 11:11:49 GMT

Explanation:

if the webpage contains a java script "detection_as3.swf", wich redirects to webpage "https://secure.skype.com", PA firewall this connection consider as a "skype" application. Case closed.