Deciphering 5G security (Part 2). The one not about the elephant but O-RANgutan in the room.
16 November 2023 - Reading time: 9 minutes
When our countless mobile devices connect to the nearest cell tower, communication occurs over the radio access network (RAN). The RAN facilitates air interface connections to the tower, which then routes signals via fibre or wireless backhaul to the heart (core) of the telecommunication network.
Traditionally, RANs have been proprietary in nature, integrated solely with individual equipment manufacturers' systems (like Ericsson, Nokia, Huawei, etc.). So, in a typical MNO's dream, they pay an insane amount of money to the vendor, then unpack a huge delivery box(s), turn the key and magically everything works. At least in theory. Truth or not, it's all in the past.
Why O-RAN?
In contrast, Open RAN (or: O-RAN) supports interoperability through standardised interfaces that enable network operators to incorporate multi-vendor sub-components like remote radio heads and distributed units. This new architecture aims to achieve three primary objectives.
- It pursues "cloudification" (oh, I really don't like this word for some reason) through disaggregated and software-based network functions that can leverage the beauty of modern cloud-native computing platforms.
- O-RAN supports open internal interfaces between network components, naturally, including standards defined by 3GPP. This objective seeks to define standardised communication protocols that enable interoperability across a diverse set of O-RAN component suppliers.
- O-RAN facilitates increased intelligence and automation. By incorporating advanced capabilities like AI/ML, it is now possible to better automate the management and orchestration of RAN resources.
This shift to disaggregated and interoperable RAN architectures inevitably introduces more flexibility and choice. However, it also seriously complicates network configurations due to the integration of many varied third-party elements, of course, coming from different vendors. As a result, the "default" security risk profile for wireless networking is severely altered under O-RAN deployments, with orchestration and segmentation challenges that previously did not exist within closed, proprietary implementations.
I think no one is surprised that there was someone who desired to put it all in order. And this heavy job was taken by the O-RAN Alliance - a group of mobile operators, vendors and researchers working to define that whole open and intelligent RAN ecosystem. The Alliance develops standards and specifications for open interfaces between network components to facilitate that much-needed multi-vendor interoperability. It also establishes reference architectures and designs for O-RAN elements. I say they are generally doing a really good job and deliver tons of useful documentation. However, we should also admit that this task is complex and all the standards go through an iterative process, sometimes lagging behind the urgent needs of the telecommunication industry. And this leaves some space for (hopefully constructive) critique. In 2021, Germany's Federal Cyber Security Authority conducted a risk assessment of the O-RAN Alliance's standards and architectural framework. Their analysis considered requirements around confidentiality, integrity, accountability, availability and privacy from the perspective of end users, network operators, and national interests. Surprisingly (or not), the results indicated e.g., that some interfaces and components specified in O-RAN could have almost immediately introduced various medium to high-security risks "by design"! Also, well-known zero-trust and "security by design" practices also did not seem to factor strongly enough into the specifications. But, luckily, everything evolves and the existing O-RAN specifications in 2023 are much more robust and truly leading the way.
Unfortunately, it does not mean that there are no more security risks for O-RAN.
In 2022 EU published a report on the security of O-RAN. The report outlined some potential risks, such as, e.g., a much wider attack surface resulting from the disaggregated architecture. With more vendors and interfaces involved, this means that there are increased opportunities for exploitation. Additionally, the O-RAN components could have various misconfiguration issues and those flaws may have greater impacts as well, given the shared infrastructure approach and resource pooling across network functions. Not surprisingy, this time, the report also raised concerns about O-RAN security not being sufficiently prioritised from the beginning. Some researchers are even attributing this to slower O-RAN adoption in Europe, e.g., compared to Japan.
Let's summarize the key O-RAN security risks.
- Dependence on cloud infrastructure introduces multiple new avenues of attack and single points of failure that challenge O-RAN secure management at scale.
- A multi-vendor ecosystem with diverse, interoperable systems complicates coordination, visibility, authentication and change management across the disaggregated architecture.
- Legacy O-RAN components manufacturers are still building core security capabilities as they transition to software-defined models, potentially leaving early-generation (legacy) systems exposed and vulnerable.
- Incorporation of third-party open source code brings many risks like missed/overlooked vulnerabilities or even backdoors waiting quietly in depths of shared libraries outside of operator purview.
- Utilisation of shared spectrum for critical access broadens the potential attack surface and raises risks of availability issues from interference or DoS of the shared resources.
How to ensure O-RAN is secured?
Follow the cybersecurity best practices. The EU has released several documents in recent years highlighting cybersecurity challenges for next-generation telecommunications infrastructure, such as EU Toolbox and various subsequent risk reports (google: 5G ENISA). All of them called attention to issues that will need ongoing mitigation as 5G networks evolve. Security concerns related to Open RAN architectures are actively being evaluated both within standards development forums as well as broader industry discussions. The security risks could be greatly reduced if the best practices are in place, such as security by design, adopting compliance standards, conducting regular risk assessments, configuration management, minimizing attack surface area, proper patch management, monitoring and logging and incident response planning.
Control your supply chain and buy O-RAN components from trusted vendors only. Let's start from this: leading vendors always invest heavily in security R&D and integrate defences proactively into new product designs. "Security-by-design" is not just a nice slogan for them. Trusted vendors also are much less likely to accidentally introduce malware or backdoors in hardware/software components during development and manufacturing. This automatically reduces many supply chain risks. Established vendors typically have dedicated security teams and processes for identifying vulnerabilities and issuing patches/updates - this level of security maturity is lacking in some smaller component makers. Last but not least: trusted vendors also follow international security standards and regulations. Their components are more likely to be compliant with requirements regarding privacy, encryption, authentication etc. out of the box.
Conduct thorough and regular security assessments. This means regular penetration testing aiming to find weaknesses before attackers can at the device level, assembled subsystems and system levels. Penetration testing can greatly help to improve O-RAN security by ticking these boxes:
- Identify hard-to-find vulnerabilities: Penetration tests actively try to exploit systems to uncover O-RAN security weaknesses before attackers do. This allows issues to be remediated. Prevention is always better than cure.
- Validate defences: Thorough testing puts O-RAN implementations through real-world attack simulations to ensure controls and countermeasures are functioning as intended.
- Surface misconfigurations: Pentests often discover vulnerabilities created by improper configurations, outdated software, or unclear access policies.
- Test patches: Repeated testing confirms security updates and new versions close previously identified vulnerabilities as intended.
- Evaluate risk exposure: Test results provide insight into the most severe weaknesses to prioritize remediation of the highest risks first.
- Stress test systems: Pushing systems to their limits through various exploit methods helps validate performance and resiliency under duress.
- Verify segmentation: Tests determine if control measures properly separate domains to contain lateral movement if one is breached.
- Audit suppliers: Pentests of third-party components validate suppliers' claims before integration into an operator's precious network.
Forewarned is forearmed.
While the benefits of O-RAN in terms of flexibility, optimisation, and cost savings are undeniable, it is critical that network operators and other stakeholders carefully consider the cybersecurity challenges that an open and virtualised architecture introduces. As we have discussed, the multi-vendor ecosystem, reliance on cloud infrastructure, use of open-source code, and increased complexity all contribute to a larger potential attack surface. However, by enforcing best practices many of these risks can be successfully mitigated. Those who embrace O-RAN by prioritising security from the start will be best positioned to reap the rewards of innovation while ensuring the resilient defence of their precious critical network infrastructure. As they used to say in Polish: "przezorny zawsze ubezpieczony" or "forewarned is forearmed".