AppID Rule with Service "any"

[wassim.bejaoui]

Hello,

I want to now the risks of allowing an application with any services.

Below an example. Thank you in advance

Kind regards.

[reaper · Accepted solution]

The 'risk' is low since you do filter on application and have security profiles in place

It would be recommended and best practice to use "application-default" instead of "any" in most cases, because it is highly unusual and maybe even suspicious for any application to be detected on a different port than their default (why would DNS be transmitted over any other port than 53?)

applications using a different port are either badly configured (and do you want to allowed badly configured services to pass through) or being used for reconnaissance or exfiltration

[wassim.bejaoui]

Hello, Reaper,

I thank you for your quick response.

Can you give me a real use case of exfiltration or reconnaissance in this type of rule.

Best regards.

[reaper]

typically proxies and other protection mechanisms listen in on the default ports of applications, an attacker may do a port scan to find open ports or use legitimate connections to see if 'ports are open'

if a non-standard port is open, it is very likely the 'target' is not scanning properly for threats, so information can be sent out through that port to avoid detection

the fact that there's applications in your policy will make this a lot harder, but why allow it in the first place