From Bugs to Blackholes: The Wild World of Flowspec in Network Security

In today’s interconnected world, internet security isn't just important - it’s essential. With the relentless rise of Distributed Denial of Service (DDoS) attacks, keeping networks safe is a never-ending challenge, hence you may have seen the launch of our new DDoS mitigation platform earlier last year. However, RETN has a powerful, old friend - Flowspec, a protocol with a colourful 20-year history that’s still defending (and surprising) people with its capabilities.

Flowspec: The Protocol That Took Its Time

Despite being around for nearly two decades, Flowspec is far from the industry default. In fact, many ISPs still haven’t invited Flowspec to the cybersecurity party. Some vendors have only recently added support for Flowspec, leaving ISPs playing catch-up on upgrades. Lucky for RETN, we’ve been a step ahead - thanks to Juniper Networks, our routers were ready for Flowspec from day one. We’ve been able to protect our network (and our clients’ nerves) from UDP flood attacks without waiting around for the competition to catch on.

Early Bugs and Blackholes: Flowspec’s Growing Pains

When Flowspec first appeared, there were more than a few bugs. One particularly memorable story from an ISP (not RETN, thankfully!) involved a misconfigured rule that accidentally blocked all TCP packets port 443 - essentially blackholing secure web traffic across their network. While it wasn’t a full-scale BGP leak disaster, it was an epic reminder that with great power comes great responsibility. Today, with careful configuration and thoughtful rule design, Flowspec has become the bouncer at our firewall’s door, keeping the malicious traffic at bay.

Smarter Filtering at the Edge of the Network

Unlike traditional BGP (Border Gateway Protocol), which just handles routes, Flowspec goes deeper, using TCP and UDP headers and other packet details to create precise traffic filtering rules. This makes it a champion at managing DDoS protection for attacks like UDP floods - a common attack type where servers are bombarded with fragmented traffic, forcing them to reassemble packets. With Flowspec, RETN intercepts and discards suspicious traffic before it even reaches our firewalls, acting as a kind of preemptive bouncer and saving our firewalls from a flood of needless processing.

Beyond Standard: RETN’s Custom Flowspec Validator

The standard Flowspec validation rules had their limits, so RETN took matters into its own hands. We developed a custom validator that enforces Flowspec’s checks, making sure that each rule is rigorously vetted before being applied. Think of it as our home-grown "hacker" tweak, optimising Flowspec to fit the unique needs of our network. This custom approach ensures that even if the RFC standards don’t catch a mismatch, our validator does.

The Battle Strategy: Clever Rule Ordering and Traffic Management

Deploying Flowspec isn’t just about turning it on, rules should be carefully planned; moreover, like in traditional firewall rules, order also matters, meaning that Flowspec filters act in a strategic sequence. Therefore, you can send instructions to RETN’s border routers to match packets with SYN flag first, then drop packets with particular lengths, and so on. It’s like a network defence “choose-your-own-adventure” game, but for packets - flows have to fight their way through a series of cleverly ordered filters, ensuring that threats are neutralised efficiently.

Scalable Defence, Distributed Filtering

One of the biggest advantages of Flowspec is its scalability. Every router in the network can participate in cleaning, which eliminates the capacity limitation related to firewall devices or scrubbing servers. You can configure/import rules on a single router, but then it will be distributed across the whole network and optionally beyond. So, the whole network turns out to be an actor in traffic mitigation, not only dedicated devices. If necessary, the updated rule can be distributed the same way, which is much easier than the orchestration of a bunch of firewalls.

Open-Source Power

There are a lot of various tools related to traffic data collection, analysis and threats detection. Some of them are proprietary and expensive, but there are also some open-source solutions.

Since Flowspec is an RFC-standardised feature that works on standard BGP protocol, it allows very smooth and easy integration to various systems. And these monitoring tools get capability not only to look but also to perform some actions based on their observations.

The Evolution of Flowspec and Support for IPv6

Initially, Flowspec was limited to IPv4, but today it’s fully compatible with IPv6 - future-proofing our security strategy as the internet expands. Combined with network automation and advanced routing protocols, RETN’s Flowspec implementation is ready to handle both today’s and tomorrow’s challenges. For us, IPv6 support is essential, especially as more customers require this level of readiness in a secure, scalable internet experience.

Monitoring the Battle: Keeping Tabs on Flowspec’s Impact

To keep our network safe, we rely on robust network monitoring tools like SNMP and Zabbix to track Flowspec’s real-time impact on traffic. When a threat emerges, Flowspec intercepts it at the edge, feeding data back to our monitoring systems. This comprehensive oversight ensures that every filtered packet and discarded UDP flood is accounted for, allowing us to constantly refine and improve our approach to security.

The Bottom Line: Flowspec is RETN’s Edge in Cybersecurity

As cyber threats continue to evolve, Flowspec remains one of RETN’s most essential tools for BGP-based traffic management and automated DDoS protection. It’s a protocol that’s taken its time to catch on, but it’s proving its worth as a critical asset for network security. From keeping our routers safe to filtering floods before they reach our firewalls, Flowspec is not just a tool - it’s a strategic part of our approach to resilient connectivity.

In the ever-changing world of internet security, RETN’s adoption of Flowspec stands out as a bold move to defend against attacks while optimising traffic flow for a seamless customer experience. And as the threats grow, so does our commitment to deploying innovative, powerful solutions to protect our network and yours.

Explore the full portfolio of RETN DDoS protection services.