IP-Intelligence and IP-Shunning
Dear Reader,
With this article we have arrived at the “last” layer of protection, which is actually the first one from the hud-chain point of view: Blocking on the IP layer.
The idea is rather simple: When you know that an IP address (or multiple IP addresses) is doing bad things, you block them as early as possible at the speed of line.
IP-Intelligence Policy
You can create IP-Intelligence (IPI) policies, which describe what should happen (Drop or Allow) with IPs (source or destination) belonging to a specific category. BIG-IP already has a bunch of pre-defined categories, but you can also add your own.
Figure 1: Example on an IPI-Policy
Important: A great benefit of using this, is that the “Drop” action is done on the FPGA level, which means in hardware. Basically, as soon as a packet hits the BIG-IP. But this is only possible when you set the logging to “No” (no logging, only dropping) or “Limited”. “Limited” means that some packets get leaked into software (CPU) for dropping them there and then they can be logged here as well. By default, every 256th packet goes into software when logging is set to “limited”. This is controlled by the sys db variable “dos.blleaklimit”. You can modify it to values like 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023, and so on. The default value is 255.
When you set the logging to “Yes”, then all packets will get logged, because the action (Drop) is done always in software.
My recommendation is to use “Limited” logging to enable FPGA support for this feature. This is also what we call “shunning” when we drop on FPGA level.
You can create multiple policies and assign them to different contexts: VS/PO or Route Domains to have individual configurations for your protected objects (services, networks, etc.) and you can also assign an IPI policy to the global level of BIG-IP, which means this will be executed first and for the whole box. Even when you want to block via IPI only on VS/PO level, my recommendation is to have a global IPI policy attached. It can be empty.
Figure 2: Global Policy assignment
Figure 3: Per VS/PO Policy assignment
Figure 4: Per Route Domain Policy assignment
Order of Mitigation
Mitigation using the hardware (FPGA) is always done first. Next, traffic goes into software and can be dropped here as well. For IPI the following order takes place. Note that IPI mitigation done on Route Domain level is always in software.
Figure 5: Mitigation Order
How to get information about “bad” IPs?
There are multiple options available.
One is to use an external service (3rd party), which does the categorization of IPs based on their reputation. If you have the IP Intelligence feature licensed, the information is being updated every 5 minutes.
Another one is to use BIG-IP to automatically identify “bad actors” via DoS vectors. In my article Increasing accuracy using Bad Actor and Attacked Destination detection, I described how that works and for what it is useful for.
But when BIG-IP identifies “bad actors” and this source IP(s) are behaving aggressive for a configurable amount of time, then it may make sense to drop everything coming from this IP(s) for a specific time interval.
Figure 6: Bad Actor Detection
In this example, the IP(s) which are identified as bad actors and behaving “bad” for 30 seconds get added to the category “denial_of_service” for 600 seconds. Once the “duration time” is over, they get released from the category and the process starts from the beginning, if they are still “bad”.
Drop Attacked Destination
Another use case to carefully consider is to drop based on attacked destination. Here you can drop all traffic going to a specific destination which is under attack. True, you stop the attack hitting the target, but you also drop all legitimate traffic going there, which would be a great success for the attacker.
But, of course, if for whatever reason the attack would potential bring the BIG-IP to its knees this is an option you can choose. You would loose the destination that is under brutal attack but at least you safe all other services on the BIG-IP from being impacted.
Figure 7: Attacked Destination Detection
Use your up-stream router
Think of the following scenario: An attack is about to saturate your Internet-pipe. You mitigate the bad actors on BIG-IP, but your pipe is still full. Why not “signal” the information of bad actors to your upstream router and drop the attackers already there, even before your pipe gets saturated?
This is what you can do with using Remote Triggered Black Hole routing (RTBH) or Flowspec.
By enabling “Allow External Advertisement” within your “Bad Actor Detection” or “Attacked Destination Detection” you can enable that functionality.
Figure 8: External Advertisement
I will cover the topic on how to use the Blacklist Publisher to “signal” bad actors including an action (Drop, Rate-limit, DSCP) to an upstream router via RTBH or Flowspec in a dedicated article. I will also explain in the same article how to use the “Scrubbing profile” to execute an action (redirect, rate-limit, DSCP, drop) on networks, PO/VS when these objects reach a certain bandwidth utilization.
More options to add bad actors into categories
Returning to how you can add IP(s) into categories. In addition to the already discussed options of using F5 subscription service and DoS vectors you can also add manually IPs. You may have your own sources and want to add this information into the categories. Here you have multiple options again.
GUI
On the Blacklist Categories page, you can manually add/delete IPs for a selected category.
Figure 9: Add IP/Geo/FQDN to categories
Feed List
You can create your own Feed List using HTTP(s) or FTP to regularly download a file and update your categories.
Figure 10: External Feed List
Don´t forget to then enable your Feed List within your IPI-Policy!
Figure 11: Enable Feed Lists
TMSH
Using tmsh you can also add IPs to categories. Here is an example:
$ tmsh run security ip-intelligence category name denial_of_service ip-ttl add { 123.123.123.123,300 }
Rest-API
Another way is to use Rest-API. Here is an example:
$ curl -sk -u sVen:mySecrectPW -H "Content-Type: application/json" -X POST -d '{"command":"run","utilCmdArgs":"name denial_of_service ip-ttl add {123.123.123.123,300}"}' https://mgmnt-address-big-ip/mgmt/tm/security/ip-intelligence/category/ | python -m json.tool
Whitelist IPs for IPI/shunning
If you want to whitelist IP(s) from not being shunned on IPI level, you need to add this IP(s) to the “whitelist” category. Please we aware that this only works when you use an external feed to add the IP(s).
Figure 12: Feed List Properties
More useful CLI commands
To get an idea on hits per category, you can use a “tmctl” command:
# tmctl -w 180 ip_intelligence_stat
It gives you an overview of hits per context, category and drop list type.
Figure 13: Stats for categories
Here you can also see that you can not only drop based on IP. You can also use GEO information and FQDN.
If you want to verify the status of an IP, you can use this command:
# tmsh show security ip-intelligence info address <ip-address>
Figure 13: Example of status of a GEOIP
Conclusion
IPI/shunning is a very effective and hardware driven way of blocking traffic based on IP information. Especially on amplification and reflection attacks it is a very useful because you are mostly able to identify IP addresses causing the high load. Often operators do also block traffic from countries on which they are sure they do not communicate with for specific services.
After finishing the explanation of this last (first) mitigation layer, you hopefully have a better understanding on how F5 L3/4/DNS DDoS mitigation works. Hardware (FPGA) support is an essential element of successful blocking high packet rates. These high-performance chips get dynamically programmed via the “smart” component, the software which runs on CPU, and which also needs to be protected. Therefore, you can configure the DoS mitigation mechanism for protecting your services (server, network, …) behind the BIG-IP, but also BIG-IP itself!
Figure 14: Multi-layer DDoS mitigation architecture
F5 also provides the ability to protect with hardware (FPGA) support in virtualized environments. Since more and more data center go virtual, the requirement of running DDoS mitigation in virtualized environments has increased. But, because FPGA support is needed for this type of DDoS mitigation, since CPU alone is usually not powerful enough, it can present a problem. Together with Intel F5 provides a strong solution. This solution uses SmartNICs (network card with FPGA on board) within your Hypervisor. DHD (DDoS Hybrid Defender) and AFM (Advanced Firewall Manager) can program these FPGAs in basically the same way as it can be done on dedicated Hardware appliances. This again gives you the power needed for DDoS mitigation, plus the flexibility of virtualized environments. If you are interested in learning more about this, I would like to recommend the article of my colleague Ryan Howard: https://devcentral.f5.com/s/articles/Mitigating-40Gbps-DDoS-Attacks-with-the-new-BIG-IP-VE-for-SmartNICs-Solution
My next article will focus on logging and reporting DDoS events. Together, my colleague Mohamed Shaath and I created a DDoS Dashboard including DDoS statistics visibility on all vectors based on an ELK stack. We will share in that article how to install and use it.
Thank you, Sven Mueller
