Difference between app base rule and service base rule.

[OsamaKhan]

Hi All,

Just some queries,

1) what is the difference between the App base rule and Service base rule?

2) For security purpose which one is a more secure app or service base rule?

3) What is the benefit of using App base rules?

Thanks in advance.

[BPry · Accepted solution]

@OsamaKhan,

1) what is the difference between the App base rule and Service base rule?

Service is only looking at layer-4, so if you open 25/tcp for example expecting to only allow SMTP traffic that doesn't really work. The only thing you're doing is allowing traffic to the specified host on 25/tcp.

App-ID is all signature based, so if you allow SMTP with application-default you'll only be allowing SMTP traffic. If that app-id's signature picks up anything else, the traffic won't match that rulebase entry. 

2) For security purpose which one is a more secure app or service base rule?

It's always going to be App-ID. App-ID is checking to make sure that the traffic that you're trying to allow is what is actually being identified. If you simply specify any application on a service object you're just opening a port. 

3) What is the benefit of using App base rules?

You're verifying that what you are trying to allow is what is actually being passed. If the traffic signature matches an app-id that you aren't allowing the traffic will be dropped. 

[OtakarKlier · Accepted solution]

Hello,

Just to expand on question 3 a bit and what BPry already mentioned. Lets say you have a policy where you only want your internal DNS or domain controllers to access DNS from the internet using a secure DNS provider. Your Application based policy would ensure that the internal DNS servers are actually using DNS to go to the external secure DNS provider. This would prevent a malicious actor from exfiltrating data out from any system using port 53 or DNS.

Hint: Please do this as it is very secure and often overlooked.

Cheers!