Identify Security Policy Rules with Unused Applications
Policy Optimizer finds Security policy rules that specify applications not seen on your network so you can remove the unused apps to reduce the attack surface.
If you have application-based Security policy rules that allow a large number of applications, you can remove unused applications (applications never seen on the rules) from those rules to tighten them so that they only allow applications actually seen in the rule’s traffic. Identifying and removing unused applications from Security policy rules is a best practice that strengthens your security posture by reducing the attack surface.
- Identify Security policy rules that have unused applications.displays all application-based rules configured with applications that aren’t in use on the network—that is, rules configured to allow more applications than the number of applications actually seen on those rules.PoliciesSecurityPolicy OptimizerUnused AppsThe number ofApps AllowedandApps Seenare updated approximately every hour, so if you configure applications on a rule and don’t see as manyApps Allowedas you expect, check again after about an hour. Depending on the firewall’s load, it may take longer than one hour for these fields to update.
- Prioritize which rules with unused applications to modify first.enables you to sort rules without affecting their order in the rulebase and provides other information that helps you prioritize rules to clean up based on your business goals and risk tolerance.PoliciesSecurityPolicy OptimizerUnused Apps
You can also clickTraffic (Bytes, 30 days)to sort by the amount of traffic a rule has seen over the last 30 days. Use this information to prioritize which rules to modify first. For example, you can prioritize rules with the largest difference betweenApps AllowedandApps Seenand that also have the mostDays with No New Apps, because those rules have the greatest number of unused applications and are the most mature.
- The difference betweenApps Allowed(the number of applications the whitelist rule allows) andApps Seen(the number of whitelisted applications actually seen on the rule) shows how many applications are configured on each rule but not actually seen on the rule, which indicates to what extent the rule is over-provisioned. ClickApps Allowedto sort by the number of applications allowed in a rule and clickApps Seento sort by the number of applications actually seen on a rule.
- Days with No New Apps(click to sort) shows you the number of days since the last time a new application hit the rule. This indicates how likely it is that the rule is mature and won’t see any applications that haven’t already been seen. The longer theDays with No New Apps, the less likely that new applications will hit the rule and the more likely that you know all the applications the rule allows.
- CreatedandModifieddates also help determine whether a rule has matured enough to understand whether applications not seen on the rule may be seen at a later date or if the rule has seen all the applications expected to hit the rule. The longer the time since a rule wasModified, the more likely the rule is mature. (IfCreatedandModifiedare the same, the rule hasn’t been modified.)
- Hit Count—Displays rules with the most matches over a selected time frame. You can exclude rules for which you reset the hit counter and specify the exclusion time period in days. Excluding rules with recently reset hit counters prevents misconceptions about rules that show fewer hits than you expect because you didn’t know the counter was reset.
- Review theApps Seenon the rule.OnUnused Apps, clickCompareor the number in theApps Seencolumn to openApplications & Usage, which shows the applications configured on the rule (Apps on Rule) and theApps Seenon the rule.
Pink-shaded applications configured on the rule may be unused applications, although pink-shaded container apps may have individual applications in use. Consider removing pink-shaded applications to reduce the attack surface. Take into account periodically used applications, such as for quarterly or annual events, which may look unused if you don’t examine a long enough time frame.Timeframeallows you to select the time frame for theApps Seenon the rule. SelectAnytimeto see every application seen over the life of the rule. Depending on theCreatedorModifieddate in theNo App Specifieddialog and the time between periodic events, the rule may not have been on the firewall long enough to see all periodically used applications.
- The number next toApps Seen(12 in this example) is the number of applications actually seen on the rule. Keep in mind that it takes at least one hour to updateApps Seen.
- The number next toApps on Rule(32 in this example) is how many applications are configured on the rule, which is calculated by counting each application in a container app (but not the container app itself—if you configure a container app on the rule, the rule allows the container app’s individual applications). However, theApplicationslist shows only the applications manually configured on the rule, so when you configure a container app on a rule,Applicationsonly shows the container app, not the individual applications in the container (unless you also manually configure the individual applications on the rule). For this reason, the number ofApps on Rulemay not be the same as the number of applications in theApplicationslist.
- The pink-shadedApps on Ruleare either:
- Applications configured on the rule but no matching traffic has been seen on the rule, so the application hasn’t been seen on the rule.
- Container apps, even when their individual applications have been seen on the rule. For example, if a rule configured with the container app active-directory sees traffic from the active-directory-base individual application, the container app is shaded pink even though one of the container app’s individual applications was seen on the rule.
- Click the number next toApps on Rulefor a pop-up dialog that shows all of the individual applications on the rule. BecauseApps on Rulelists container apps but not the individual applications in those container apps (unless the individual applications were manually configured on the rule), the pop-up dialog may show a different number of applications than theApplicationslist underApps on Rule.In the following example, 7 applications have been seen on the rule and the rule allows 50Apps on Rule. The linked in container app is configured on the rule and the rule sees traffic from the individual applications linkedin-apps, linkedin-base, linkedin-editing, linkedin-intro, linkedin-mail, and linkedin-posting.Apps on Ruleshades the container app linkedin (which is configured on the rule) pink. It does not show the individual applications, which are not specifically configured on the rule. When you click theApps on Rulenumber, the pop-up dialog expands the container app to display the individual applications, but not the container app itself.You cannot add or delete applications from the pop-up dialog.
- The unshadedApps on Ruleare applications that have been seen on the rule.
- Remove unused applications from the rule.Delete(orAdd) applications inApps on Ruleto remove (or add) applications manually, orMatch Usageto add theApps Seenon the rule and delete applications for which no matching traffic has been seen on the rule with one click.To remove applications from the rule manually, select the pink-shaded applications fromApps on RuleandDeletethem. Ensure that none of the pink-shaded applications are required for periodic events before you remove them from the rule. (You can still add or delete applications on the Security policy rule’sApplicationtab, but unused applications aren’t shaded pink.)Match Usagemoves theApps Seenon the rule toApps on Ruleand removes all unused (pink-shaded) applications from the rule.
- Committhe configuration.
- Monitor updated rules and listen to user feedback to ensure that updated rules allow the applications you want to allow and don’t inadvertently block periodically used applications.The number ofApps AllowedandApps Seenare updated approximately every hour. After you remove all of the unused applications from a rule, the rule remains listed inuntil the firewall updates the display. When the firewall updates the display and the number ofPoliciesSecurityPolicy OptimzerUnused AppsApps Allowedis the same as the number ofApps Seen, the rule no longer displays in theUnused Appsscreen. However, depending on the firewall’s load, it may take longer than one hour for these fields to update.
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