Configure the Sinkhole IP Address to a Local Server on Your
By default, sinkholing is enabled for all Palo Alto Networks DNS signatures, and the sinkhole IP address is set to access a Palo Alto Networks server. Use the instructions in this section if you want to set the sinkhole IP address to a local server on your network.
You must obtain both an IPv4 and IPv6 address to use as the sinkhole IP addresses because malicious software may perform DNS queries using one or both of these protocols. The DNS sinkhole address must be in a different zone than the client hosts to ensure that when an infected host attempts to start a session with the sinkhole IP address, it will be routed through the firewall.
The sinkhole addresses must be reserved for this purpose and do not need to be assigned to a physical host. You can optionally use a honey-pot server as a physical host to further analyze the malicious traffic.
The configuration steps that follow use the following example DNS sinkhole addresses:
IPv4 DNS sinkhole address—10.15.0.20
IPv6 DNS sinkhole address—fd97:3dec:4d27:e37c:5:5:5:5
- Configure the sinkhole interface and zone.Traffic from the zone where the client hosts reside must route to the zone where the sinkhole IP address is defined, so traffic will be logged.Use a dedicated zone for sinkhole traffic, because the infected host will be sending traffic to this zone.
- Selectand select an interface to configure as your sinkhole interface.NetworkInterfaces
- In theInterface Typedrop-down, selectLayer3.
- To add an IPv4 address, select theIPv4tab and selectStaticand then clickAdd. In this example, add 10.15.0.20 as the IPv4 DNS sinkhole address.
- Select theIPv6tab and clickStaticand then clickAddand enter an IPv6 address and subnet mask. In this example, enter fd97:3dec:4d27:e37c::/64 as the IPv6 sinkhole address.
- ClickOKto save.
- To add a zone for the sinkhole, selectand clickNetworkZonesAdd.
- Enter zoneName.
- In theTypedrop-down selectLayer3.
- In theInterfacessection, clickAddand add the interface you just configured.
- Enable DNS sinkholing.By default, sinkholing is enabled for all Palo Alto Networks DNS signatures. To change the sinkhole address to your local server, see Step Verify the sinkholing settings on the Anti-Spyware profile. in Configure DNS Sinkholing for a List of Custom Domains.
- Edit the security policy rule that allows traffic from client hosts in the trust zone to the untrust zone to include the sinkhole zone as a destination and attach the Anti-Spyware profile.Editing the Security policy rule(s) that allows traffic from client hosts in the trust zone to the untrust zone ensures that you are identifying traffic from infected hosts. By adding the sinkhole zone as a destination on the rule, you enable infected clients to send bogus DNS queries to the DNS sinkhole.
- Select an existing rule that allows traffic from the client host zone to the untrust zone.
- On theDestinationtab,Addthe Sinkhole zone. This allows client host traffic to flow to the sinkhole zone.
- On theActionstab, select theLog at Session Startcheck box to enable logging. This will ensure that traffic from client hosts in the Trust zone will be logged when accessing the Untrust or Sinkhole zones.
- In theProfile Settingsection, select theAnti-Spywareprofile in which you enabled DNS sinkholing.
- ClickOKto save the Security policy rule and thenCommit.
- To confirm that you will be able to identify infected hosts, verify that traffic going from the client host in the Trust zone to the new Sinkhole zone is being logged.In this example, the infected client host is 192.168.2.10 and the Sinkhole IPv4 address is 10.15.0.20.
- From a client host in the trust zone, open a command prompt and run the following command:C:\>ping<sinkhole address>The following example output shows the ping request to the DNS sinkhole address at 10.15.0.2 and the result, which isRequest timed outbecause in this example the sinkhole IP address is not assigned to a physical host:C:\>ping 10.15.0.20Pinging 10.15.0.20 with 32 bytes of data: Request timed out. Request timed out. Ping statistics for 10.15.0.20: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss)
- On the firewall, selectand find the log entry with the Source 192.168.2.10 and Destination 10.15.0.20. This will confirm that the traffic to the sinkhole IP address is traversing the firewall zones.MonitorLogsTrafficYou can search and/or filter the logs and only show logs with the destination 10.15.0.20. To do this, click the IP address (10.15.0.20) in theDestinationcolumn, which will add the filter (addr.dst in 10.15.0.20) to the search field. Click the Apply Filter icon to the right of the search field to apply the filter.
- Test that DNS sinkholing is configured properly.You are simulating the action that an infected client host would perform when a malicious application attempts to call home.
- Find a malicious domain that is included in the firewall’s current Antivirus signature database to test sinkholing.
- SelectDeviceDynamicUpdatesand in theAntivirussection click theRelease Noteslink for the currently installed antivirus database. You can also find the antivirus release notes that list the incremental signature updates under Dynamic Updates on the Palo Alto Networks support site.
- In the second column of the release note, locate a line item with a domain extension (for example, .com, .edu, or .net). The left column will display the domain name. For example, Antivirus release 1117-1560, includes an item in the left column named "tbsbana" and the right column lists "net".The following shows the content in the release note for this line item:conficker:tbsbana 1 variants: net
- From the client host, open a command prompt.
- Perform an NSLOOKUP to a URL that you identified as a known malicious domain.For example, using the URLtrack.bidtrk.com:C:\>nslookuptrack.bidtrk.com Server: my-local-dns.local Address: 10.0.0.222 Non-authoritative answer: Name: track.bidtrk.com.org Addresses: fd97:3dec:4d27:e37c:5:5:5:510.15.0.20In the output, note that the NSLOOKUP to the malicious domain has been forged using the sinkhole IP addresses that we configured (10.15.0.20). Because the domain matched a malicious DNS signature, the sinkhole action was performed.
- Selectand locate the corresponding threat log entry to verify that the correct action was taken on the NSLOOKUP request.MonitorLogsThreat
- Perform a ping totrack.bidtrk.com, which will generate network traffic to the sinkhole address.
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