The O-RAN Near-Real-Time RAN Intelligent Controller (RIC) relies on strict isolation between xApps to enforce security boundaries as recommended by O-RAN WG11. In this paper, we demonstrate that the current O-RAN Software Community (O-RAN SC) reference implementation violates these assumptions. We identify two previously undocumented vulnerabilities in the Subscription Manager that enable covert communication between network-isolated xApps. The first channel redirects subscription responses to unintended recipients, enabling low-rate data leakage without special privileges. The second abuses a shared debugging endpoint to establish a high-throughput, bidirectional covert channel. We experimentally evaluate both channels on a deployed O-RAN SC Near-RT RIC and discuss their security impact and mitigations.

Quantum Key Distribution (QKD) promises information-theoretic secrecy by leveraging quantum physics, yet practical deployments depend heavily on a classical, packet-switched control channel for timing, synchronization, and key management. Surprisingly, this critical classical component has been largely overlooked from a network- and system-security perspective. In this paper, we present a comprehensive security evaluation of the classical channel in a commercial-grade entangled-photon BBM92 QKD deployment. We introduce Pickle-TCP, a transparent, QKD-protocol-aware fault-injection proxy that manipulates control-plane messages. Using only intercepted network traffic, we reverse-engineer the proprietary QKD protocol and uncover zero-day exploitable vulnerabilities in authentication, synchronization, and control-message handling. Leveraging this understanding, we demonstrate three concrete and repeatable attacks that disrupt authentication, silently desynchronize key pools, and halt key generation in our deployment without triggering operator-visible alarms. As a practical countermeasure, we evaluated a post-quantum-secure tunnel for the classical channel using WireGuard and Rosenpass and measured an approximately 6.6

Open-Radio Access Network (O-RAN) is the next evolutionary step in mobile network architecture and operations and the Near-Real Time RAN Intelligent Controller (Near-RT RIC) plays a central role in the O-RAN architecture as it interfaces between the orchestration layer and next generation eNodeBs. In this paper we highlight the architectural weakness of a centralized controller in O-RAN by first drawing parallels with the Software-Defined Networking (SDN) controller. We then present a two part security evaluation of two open-source Near-RT RICs (μONOS and OSC), focused on the newly introduced A1 interface of the Near-RT RIC. In the first part of our evaluation, we evaluate the supply-chain risks of μONOS and OSC using off-the-shelf open-source dependency analysis and configuration file analysis tools. In the second part, we present our run-time security testing of the A1 API implemented by μONOS and OSC using our custom O-RAN A1 Interface Testing Tool (OAITT). Our supply-chain risk analysis shows that both the open-source Near-RT RICs we evaluated have multiple dependency risks and weak or insecure configurations. We identified 211 and 285 known dependency vulnerabilities in μONOS and OSC respectively of which 82 and 190 dependencies were rated as high CVSS respectively. The A1 interface contributed to a majority of the dependency risks in both Near-RT RICs. From a security misconfiguration perspective, we identified issues concerning access control, lack of encryption and poor secret management. Our run-time testing of OSC and μONOS revealed the following. First, both Near-RT RICs lack TLS for the A1 interface. Second, malicious Non-Real Time RAN Intelligent Controller (Non-RT RIC)s or rApps that reside in the Non-RT RIC could tamper with policies installed in the Near-RT RIC which can impact the availability of the O-RAN. Third, the A1 protocol could be exploited by Non-RT RICs for covert communication via the Near-RT RIC. Fourth, the A1 implementation by μONOS was vulnerable to degradation of service attacks (10-60s response time for GET requests) and a denial of service attack, the latter has been ethically reported and a fix is underway.

Tracking users is a ubiquitous practice on the web today. User activity is recorded and analyzed on a large scale to create personalized products, forecast future behavior, and prevent online fraud. While HTTP cookies have been the weapon of choice so far, new and more pervasive techniques such as browser fingerprinting are gaining traction. This paper describes how users can be empowered against fingerprinting by showing them when, how, and who is tracking them. To this end, we conduct a systematic analysis of various fingerprinting tools to create FPMON: a browser extension to measure and rate fingerprinting activity on any website in real-time. With FPMON, we evaluate the 10k most popular websites to i) study the pervasiveness of fingerprinting; ii) review the latest countermeasures; and iii) identify the networks that foster the use of fingerprinting. Our evaluations reveal that i) fingerprinters subvert privacy regulations; ii) they are present on privacy-sensitive websites (insurance, finances, NGOs); and iii) current countermeasures cannot sufficiently protect users. Hence, we publish FPMON as a free browser extension to empower users against this growing threat.

Since caches are shared and coherent, a memory access of one process may evict from the cache another process' memory block with an address mapped to the same cache line. This property is exploited by several attacks to form side channels. We show that MAC learning in Software Defined Networks (SDNs) has a similar property in the sense that a MAC address discovered by one network device may be revoked by the discovery of the same address at another switch. This allows us to implement Macchiato, a covert channel for SDNs between any two network devices (including hosts); prior SDN covert channels required at least one malicious switch. We evaluate a prototype implementation of Macchiato and discuss how methods to improve the performance of cache side channels (such as deep neural networks) can also be used in Macchiato.

Since caches are shared and coherent, a memory access of one process may evict from the cache another process' memory block with an address mapped to the same cache line. This property is exploited by several attacks to form side channels. We show that MAC learning in Software Defined Networks (SDNs) has a similar property in the sense that a MAC address discovered by one network device may be revoked by the discovery of the same address at another switch. This allows us to implement Macchiato, a covert channel for SDNs between any two network devices (including hosts); prior SDN covert channels required at least one malicious switch. We evaluate a prototype implementation of Macchiato and discuss how methods to improve the performance of cache side channels (such as deep neural networks) can also be used in Macchiato.

QUIC is a new transport protocol over UDP which is recently became an IETF RFC. Our security analysis of the Connection ID mechanism in QUIC reveals that the protocol is underspecified. This allows an attacker to count the number of server instances behind a middlebox, e.g., a load balancer. We found 4/15 (~25%) implementations vulnerable to our enumeration attack. We then concretely describe how an attacker can count the number of instances behind a load balancer that either uses Round Robin or Hashing.

Tracking users is a ubiquitous practice on the web today. User activity is recorded and analyzed on a large scale to create personalized products, forecast future behavior, and prevent online fraud. While HTTP cookies have been the weapon of choice so far, new and more pervasive techniques such as browser fingerprinting are gaining traction. This paper describes how users can be empowered against fingerprinting by showing them when, how, and who is tracking them. To this end, we conduct a systematic analysis of various fingerprinting tools to create FPMON: a browser extension to measure and rate fingerprinting activity on any website in real-time. With FPMON, we evaluate the 10k most popular websites to i) study the pervasiveness of fingerprinting; ii) review the latest countermeasures; and iii) identify the networks that foster the use of fingerprinting. Our evaluations reveal that i) fingerprinters subvert privacy regulations; ii) they are present on privacy-sensitive websites (insurance, finances, NGOs); and iii) current countermeasures cannot sufficiently protect users. Hence, we publish FPMON as a free browser extension to empower users against this growing threat.

In this dissertation we adopt a threat model where the data center network infrastructure is potentially malicious. To describe practical threats and solutions related to malicious switches, we draw our attention to multi-tenant data center networks that i) consolidate control over the (hardware and software) switches to a logically centralized controller and ii) use virtualization techniques for multi-tenancy. Our extensive security analyses and evaluations of the design, specifications and systems of logically centralized data center network controllers reveals the following. Malicious switches can covertly bypass network-wide security policies and mechanisms via the controller. We identify three reasons for the existence of such covert channels: i) malicious switches share the logical controller, ii) lack of authentication and authorization of switches to the controller and iii) introduction of automation and programmability of the network. These channels can be reliable (TCP-based) and fast (10 Mbps). As a result malicious switches can launch several network-based attacks in the data center, e.g., to circumvent firewalls to access unauthorized data. Furthermore, our state transition and delay model of the switch-controller handshake allows us to design, implement and evaluate a covert timing channel that uses a frame-based transmission scheme for accurate and low bandwidth (20 bps) communication, e.g., to exfiltrate private keys. We also initiate the discussion of practical countermeasures, e.g., coupling TLS with the switch-controller handshake for authentication. Next, our security analysis of network virtualization architectures that use virtual switches— a key system for enforcing network isolation in multi-tenant data center networks—sheds light on the following. Increasing network functionality in the virtual switch coupled with colocating it with the hypervisor and the lack of appropriate threat models among other reasons has resulted in an insecure design. An attacker can escape host and network virtualization and compromise the entire data center as a worm. By fuzzing the packet parser of a popular virtual switch (OvS), we discovered 3 exploitable memory corruption vulnerabilities. We use just one of them in a popular cloud management system (OpenStack) to demonstrate our point: From a virtual machine (VM) we could take down hundreds of servers in a few minutes. Our measurements of the impact of software-based countermeasures that could have prevented the discovered vulnerabilities from being exploited for OvS show that maximum packet processing throughput is reduced by half in the kernel whereas the overhead in user-space is minimal (1-15%). Finally, we continue our previous work by first surveying the security landscape of 23 virtual switches and conclude that nearly all of them lack security in their design. Hence, we introduce four secure design principles for virtual switches and accordingly build a scalable prototype that prevents the virtual switch from being a liability to the (multi-tenant) data center network. The key insights from our system and performance evaluations are as

We revisit multi-tenant network virtualization in data centers, and make the case for tenant-specific virtual switches. In particular, tenant-specific virtual switches allow cloud providers to extend fine-grained billing (known, e.g., from serverless architectures) to the network, accounting not only for IO, but also CPU or energy. We sketch an architecture and present economical motivation and recent technological enablers. We also find that virtual switches today do not offer sufficient multi-tenancy and can introduce artificial performance bottlenecks, e.g., in load balancers. We conclude by discussing additional use cases for tentant-specific switches.

In this paper we describe our experience in designing and evaluating our graduate level computer security seminar course. In particular, our seminar is designed with two goals in mind. First, to instil critical thinking by teaching graduate students how to read, review and present scientific literature. Second, to learn about the state-of-the-art in computer security and privacy research by reviewing proceedings from one of the top four security and privacy conferences including IEEE Symposium on Security and Privacy (Oakland SP), USENIX Security, Network and Distributed System Security Symposium (NDSS) and ACM Conference on Computer and Communications Security (CCS). The course entails each student to i) choose a specific technical session from the most recent conference, ii) review and present three papers from the chosen session and iii) analyze the relationship between the chosen papers from the session. To evaluate the course, we designed a set of questions to understand the motivation and decisions behind the students' choices as well as to evaluate and improve the quality of the course. Our key insights from the evaluation are the following: The three most popular topics of interest were Privacy, Web Security and Authentication, ii) 33% of the students chose the sessions based on the title of papers and iii) when providing an encouraging environment, students enjoy and engage in discussions.

Private networks are typically assumed to be trusted as security mechanisms are usually deployed on hosts and the data plane is managed in-house. The increasing number of attacks on network devices, and recent reports on backdoors, forces us to revisit existing security assumptions and demands new approaches to detect malicious activity. This paper presents Preacher, a runtime network policy checker, which leverages a secure, redundant and adaptive sample distribution scheme that allows us to provably detect adversarial switches or routers trying to reroute, mirror, drop, inject, or modify packets (i.e., header and/or payload) even under collusion. Additionally, the analysis performed by Preacher is highly parallelizable. We show that emerging programmable networks provide an ideal vehicle to detect suspicious network activity. Furthermore, we analytically and empirically evaluate the effectiveness of our approach in different adversarial settings, report on a proof-of-concept implementation using ONOS, and provide insights into the resource and performance overheads of Preacher.

Multi-tenant cloud computing provides great benefits in terms of resource sharing, elastic pricing, and scalability, however, it also changes the security landscape and introduces the need for strong isolation between the tenants, also inside the network. This paper is motivated by the observation that while multi-tenancy is widely used in cloud computing, the virtual switch designs currently used for network virtualization lack sufficient support for tenant isolation. Hence, we present, implement, and evaluate a virtual switch architecture, MTS, which brings secure design bestpractice to the context of multi-tenant virtual networking: compartmentalization of virtual switches, least-privilege execution, complete mediation of all network communication, and reducing the trusted computing base shared between tenants. We build MTS from commodity components, providing an incrementally deployable and inexpensive upgrade path to cloud operators. Our extensive experiments, extending to both micro-benchmarks and cloud applications, show that, depending on the way it is deployed, MTS may produce 1.52x the throughput compared to state-of-the-art, with similar or better latency and modest resource overhead (1 extra CPU). MTS is available as open source software.

Software-defined networking is considered a promising new paradigm, enabling more reliable and formally verifiable communication networks. However, this paper shows that the separation of the control plane from the data plane, which lies at the heart of Software-Defined Networks (SDNs), can be exploited for covert channels based on SDN Teleportation, even when the data planes are physically disconnected.This paper describes the theoretical model and design of our covert timing channel based on SDN Teleportation. We implement our covert channel using a popular SDN switch, Open vSwitch, and a popular SDN controller, ONOS. Our evaluation of the prototype shows that even under load at the controller, throughput rates of 20 bits per second are possible, with a communication accuracy of approximately 90%. We also discuss techniques to increase the throughput further.

Virtual switches are a crucial component of SDN-based cloud systems, enabling the interconnection of virtual machines in a flexible and "software-defined" manner. This paper raises the alarm on the security implications of virtual switches. In particular, we show that virtual switches not only increase the attack surface of the cloud, but virtual switch vulnerabilities can also lead to attacks of much higher impact compared to traditional switches. We present a systematic security analysis and identify four design decisions which introduce vulnerabilities. Our findings motivate us to revisit existing threat models for SDN-based cloud setups, and introduce a new attacker model for SDN-based cloud systems using virtual switches. We demonstrate the practical relevance of our analysis using a case study with Open vSwitch and OpenStack. Employing a fuzzing methodology, we find several exploitable vulnerabilities in Open vSwitch. Using just one vulnerability we were able to create a worm that can compromise hundreds of servers in a matter of minutes. Our findings are applicable beyond virtual switches: NFV and high-performance fast path implementations face similar issues. This paper also studies various mitigation techniques and discusses how to redesign virtual switches for their integration.

While multi-tenant cloud computing provides great benefits in terms of resource sharing, it introduces a new security landscape and requires strong network isolation guarantees between the tenants. Such network isolation is typically implemented using network virtualization: Virtual switches residing in the virtualization layer enforce isolation, e.g., via tunnel protocols and per-tenant flow rules. The design of such switches is a very active topic: Since 2009 alone, at least 22 different designs have been introduced. Our systematic analysis of 22 virtual switches uncovers 4 security weaknesses: Co-location, single point of failure, privileged packet processing and manual packet parsing. An attacker can easily undermine network isolation by exploiting those weaknesses. Hence, we introduce 3 secure design principles to build a resilient virtual switch, thereby offering strong virtual network isolation.

Fuzz testing is an effective and scalable technique to perform software security assessments. Yet, contemporary fuzzers fall short of thoroughly testing applications with a high degree of control-flow diversity, such as firewalls and network packet analyzers. In this paper, we demonstrate how static program analysis can guide fuzzing by augmenting existing program models maintained by the fuzzer. Based on the insight that code patterns reflect the data format of inputs processed by a program, we automatically construct an input dictionary by statically analyzing program control and data flow. Our analysis is performed before fuzzing commences, and the input dictionary is supplied to an off-the-shelf fuzzer to influence input generation. Evaluations show that our technique not only increases test coverage by 10–15

As cloud computing becomes more and more prevalent, there is increased interest in mitigating attacks that target hypervisors from within the virtualized guest environments that they host. We present VDF, a targeted evolutionary fuzzing framework for discovering bugs within the software-based virtual devices implemented as part of a hypervisor. To achieve this, VDF selectively instruments the code of a given virtual device, and performs record and replay of memory-mapped I/O (MMIO) activity specific to the virtual device. We evaluate VDF by performing cloud-based parallel fuzz testing of eighteen virtual devices implemented within the QEMU hypervisor, executing over two billion test cases and revealing over one thousand unique crashes or hangs in one third of the tested devices. Our custom test case minimization algorithm further reduces the erroneous test cases into only 18.57% of the original sizes on average.

Software-defined networking is considered a promising new paradigm, enabling more reliable and formally verifiable communication networks. However, this paper shows that the separation of the control plane from the data plane, which lies at the heart of Software-Defined Networks (SDNs), introduces a new vulnerability which we call teleportation. An attacker (e.g., a malicious switch in the data plane or a host connected to the network) can use teleportation to transmit information via the control plane and bypass critical network functions in the data plane (e.g., a firewall), and to violate security policies as well as logical and even physical separations. This paper characterizes the design space for teleportation attacks theoretically, and then identifies four different teleportation techniques. We demonstrate and discuss how these techniques can be exploited for different attacks (e.g., exfiltrating confidential data at high rates), and also initiate the discussion of possible countermeasures. Generally, and given today's trend toward more intent-based networking, we believe that our findings are relevant beyond the use cases considered in this paper.

Virtual switches are a crucial component of cloud operating systems that interconnect virtual machines in a flexible manner. They implement complex network protocol parsing in the unified packet parser - parsing all supported packet header fields in a single pass - and are commonly co-located with the virtualization layer. We find that this significantly reduces the barrier for low-budget attackers to launch high impact attacks in the cloud. This leads us to introduce the virtual switch attacker model for packet-parsing , in short the vAMP attack. Using OpenStack, a cloud operating system, and Open vSwitch, a virtual switch, we demonstrate how current virtual switch designs cannot withstand vAMP. Thereby giving a weak attacker full control of the cloud in a matter of minutes