Odd traffic going out through an application-specific security rule

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Highlighted
L0 Member

Odd traffic going out through an application-specific security rule

I've got a rule that allows the following applications from any source in our trusted zone out to any destination in the untrust zone.

  • appdynamics
  • dns-over-https
  • dns-over-tls
  • github
  • ms-delve
  • net.tcp
  • ntp
  • ocsp
  • okta
  • paloalto-updates
  • paloalto-wildfire-cloud
  • pan-db-cloud
  • rtcp
  • service-now
  • skype
  • ssh
  • windows-azure
  • windows-push-notifications

The rule is set for application-default.

 

We have some legitimate traffic on our network that goes from trust to untrust with the destination port of tcp/37.

 

For some reason, this traffic is matching up to this rule.  None of the applications in the rule list tcp/37 as a default port.  Only two of those applications (skype and net.tcp) have dynamic default ports.

When the tcp/37 traffic hits this rule, the application always shows up as "insufficient-data"

 

I know what the traffic is - it is supposed to be the old "TIME" protocol.  I've actually created a rule specific for this further down the list.

 

Any idea why the traffic would match up to this rule?

Highlighted
Cyber Elite

@BSwientoniowski,

Whenever you have a rule allowing application-default the firewall is going to allow enough traffic to identify the application. So the rule that this traffic is hitting is, if I would have to make an educated guess, the first entry in your security rulebase from trust to untrust that is based off of app-id. 

Highlighted
L0 Member

Thanks for the response.  The rule that the traffic is hitting is actually the 4th rule in the list going from trust to untrust that is based off of app-id.

Highlighted
Cyber Elite

Hello,

Also as a suggestion, please use URL filtering as well as DNS sinkholes. Will make your security posture that much better.

 

Regards,

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