F5 AFM/Edge Firewall and the difference between Edge Firewalls and Next-generation Firewalls (NGFW)

Next-generation Firewalls (NGFW) have a lot of features like policies based on AD users and AD groups, dynamic user quarantine, Application/Service and Virus/Spyware/Vulnerability default or custom signatures to allow traffic only comming from specific applications that is scanned for viruses or other malware types.

A long time ago I also did not know the difference between the F5 AFM and NGFW (I even asked a question on the forum https://community.f5.com/t5/technical-forum/to-make-the-f5-afm-like-a-full-ngfw-is-there-plans-the-f5-afm-to/td-p/207685 ), so after time I understood the difference and I have made this post to clear things out 😉

NGFW truly provides a lot of nice options but where they are lacking when they are deployed at the Internet Service Providers, Mobile Operators or at the Edge of big corporate networks or private scrubbing centers as they don't have good DDOS protections or CG-NAT functions. NGFW dp have NAT capabilities but in most cases dose capabilities are limited to basic source PAT, destination NAT or Static NAT. Also at the Edge of the Network the firewall device should have high throughput and there is no need for it to work with AD users/AD groups, user/group redistribution between the firewalls or specific Applications/Services, used just by a specific company as in the case with ISP or Mobile Operators it should protect many customers with the Advanced DOS/DDOS options, to be able to do NAT that is easily traceable in the logs which IP address to which source ip which public ip was allocated (great feature for mobile or Internet providers combined with F5 PEM for user monetization and tracking) Also the Edge firewall device may need to failover to a Scrubbing center if the DDOS attack becomes too big, so this function is nice to have or to have an ip intelligence feed list to block attacks even before doing any deep inspections just based on the source or destination IP address.

This is where the F5 AFM comes into the picture as not an replacement of the NGFWs but as a complementary device that is at the Edge of the Network and filters the traffic and then the customer NGFWs do the more fine grade checks. Sometimes AFM is deployed as a server firewall together with F5 LTM/APM/aAWAF after the NGFWs for example to filter the a DDOS attack that the scrubbing center did not block as it was too small and directed to a specific destination and most scrubbing center block only really high volume attacks (most scrubbing centers can't look in the SSL data like the F5 Silverline) that can bring down the entire data center. AFM can now work with subscriber data at the ISP mobile operator level and from what I have seen the NGFW are limited in this field and they are made for internal Enterprise use, where AD groups and AD users are needed not subscriber data.

The F5 AFM capabilities that I have not seen at most NGFW are :

DOS based protections on the AFM have the option to be Fully Atomatic and to adjust their thresholds based Machne Learning (ML) learning, so there id no need for someone to constantly modify the DOS thresholds like with other DOS protection products. Also the DDOS protection has Dinamic signatures and with this feature a dynamic signature of the DDOS traffic is Automatically generated, so only the attackers to be blocked. By default the DDOS protection thresholds under "Security > DoS Protection > Device Protection " are inforced if a not more specific DOS profile is athached under the Virtual Server. The F5 AFM can be combined with the F5 Advanced WAF/ASM for full layer 3/4/7 DDOS protection and there is device named F5 DDoS Hybrid Defender that is combination between the Layer3/4 and the Layer7 protections and it is configured with a Guided Configuration Wizard. The F5 AFM has DDOS protections not only for TCP, UDP,ICMP traffic but also for HTTP, DNS and SIP protocols.

       There are great community articles about the DDOS features and their configuration that I will share:

       https://community.f5.com/t5/technical-articles/explanation-of-f5-ddos-threshold-modes/ta-p/286884

                 https://community.f5.com/t5/technical-articles/ddos-mitigation-with-big-ip-afm/ta-p/281234

              Also this link is helpfull:

              https://support.f5.com/csp/article/K49869231

The AFM can redirect the traffic to a Scrubing Center if it becomes too big and this may save some money to only use a scrubbing center if the DDOS is too big. If BGP is used the AFM will use the F5 Zebos Routing module that is like a mini router inside F5.

The previous F5 product Carrier Grade NAT is now migrated to the AFM which allows you to not only use source nat, destination nat or static nat but also to use NAT features like PBA, Deterministic NAT or PCP. The AFM can also respond to ARP requests for translated source IP addresses and this is called Proxy ARP or to intgrate with the ZebOS routin module that is like a mini router inside the F5 device to advertize the translated addresses.

Port block allocation (PBA) mode is a translation mode option that reduces CGNAT logging, by logging only the allocation and release of each block of ports. When a subscriber first establishes a network connection, the BIG-IP® system reserves a block of ports on a single IP address for that subscriber. The system releases the block when no more connections are using it. This reduces the logging overhead because the CGNAT logs only the allocation and release of each block of ports.
Deterministic mode is an option used to assign translation address, and is port-based on the client address/port and destination address/port. It uses reversible mapping to reduce logging, while maintaining the ability for translated IP address to be discovered for troubleshooting and compliance with regulations. Deterministic mode also provides an option to configure backup-members. And there is even a tool dnatutil to see the mapping of a client ip address.
Port Control Protocol (PCP) is a computer networking protocol that allows hosts on IPv4 or IPv6 networks to control how the incoming IPv4 or IPv6 packets are translated and forwarded by an upstream router that performs network address translation (NAT) or packet filtering. By allowing hosts to create explicit port forwarding rules, handling of the network traffic can be easily configured to make hosts placed behind NATs or firewalls reachable from the rest of the Internet (so they can also act as network servers), which is a requirement for many applications.

As logging the user NAT translations is mandatory this can generate a lot of logs for the Service Providers but with DNAT and PBA the needed log space is reduced as much as possible but still keeping the needed log info.

The AFM now supports some of the options of F5 PEM for Traffic Intelligence or as in the NGFW applicaion discovery or subscriber discovery and security rules based on subscribers discovered by Radius or DHCP sniffing or iRules as the NGFW have AD users and AD groups but Service and Mobile providers work with IMEI phone codes and not with AD groups/users.

https://community.f5.com/t5/technical-articles/traffic-intelligence-in-afm-through-categories/ta-p/295310

Another really wonderful feature is the IP intelligence that will protect you from bad source or destination ip addresses and with the AFM you can also feed the AFM custom list that are generated by your threat intelligence platform. The AFM and Advanced WAF/ASM can automatically place the IP addresses in a shun list that is blocked by the IP intelligence as the IP intelligence checks happen before the ASM or even the AFM in the traffic path!
There is a nice community video about this feature: https://community.f5.com/t5/technical-articles/the-power-of-ip-intelligence-ipi/ta-p/300528

The AFM also has port misuse policies or Protocol Inspection profiles that are similar the NGFW Applications/services to allow only the correct protocol on the port not just port number or IPS/Antivirus signatures. The F5 AFM Protocol Inspection is based on SNORT so you can not only block attacks but allow traffic based on the payload, for example providing access to sertain server only if the Referer header is a sertain value by writing custom signatures. It by default has many signatures and protocol RFC compliance checks. The F5 AFM protocol inspection can also be used as as more fine grade way for custom application control than the Port Misuse policies, when creating a custom signature for example to block specific User-Agent HTTP header!

One of the best features that the F5 Protocol Inspection IPS has compared even to NGFW products is to place new signatures in staging (for example after a new signature set is downloaded) for some time and to monitor how many times the signatures get triggered in that staging period before enforcing and that feature is really great.

For more information I suggest checking th e link below:

https://support.f5.com/csp/article/K00322533

https://f5-agility-labs-firewall.readthedocs.io/en/latest/class2/module3/lab4.html

https://support.f5.com/csp/article/K25265787

The F5 AFM is also a great Edge firewall for many protocols like DNS, SSH,SIP not only HTTP.The F5 AFM simiarly to the aWAF/ASM can work in a transperant bridged mode thanks to Vlan Groups, Wildcard VS and Proxy Arp, where it is invisible for the end users (https://support.f5.com/csp/article/K15099). Do not forget that tha AFM is before any other module except the IP intelligence and to decide if it will work in a firewall or ADC mode(https://support.f5.com/csp/article/K92958047). Also the order or the rules is important (Global context policies/rules > Route Domain Context > Virtual Server/Self IP > Managment) . You can even use DNS FQDN names in the security policy rules if needed and trace any issues related to Security Rules and DOS with the Packet Tester tool and with Timer policies you can allow long live connections that do not generate traffic through the firewall if needed!The Managment IP in newer versions can use AFM rules even without AFM being provisioned (https://support.f5.com/csp/article/K46122561 ), isn't that nice 😀 !

F5 supports vWire or Vlan groups, so F5 AFM or F5 DHD (DDOS Hybrid Defender) can be placed not only like a layer 3 firewall but also in Transparent/Invisible layer 2 or in case or Virtual Wire layer 1 mode.

The F5 AFM operations guide is trully a nice resource to review:

https://support.f5.com/csp/article/K38201755

Updated Jan 16, 2023

Version 5.0

application delivery

Security