The Anatomy and Facets of Dynamic Policies

Information flow policies are often dynamic; the security concerns of a program will typically change during execution to reflect security-relevant events. A key challenge is how to best specify, and give proper meaning to, such dynamic policies. A large number of approaches exist that tackle that challenge, each yielding some important, but unconnected, insight. In this work we synthesise existing knowledge on dynamic policies, with an aim to establish a common terminology, best practices, and frameworks for reasoning about them. We introduce the concept of facets to illuminate subtleties in the semantics of policies, and closely examine the anatomy of policies and the expressiveness of policy specification mechanisms. We further explore the relation between dynamic policies and the concept of declassification.Comment: Technical Report of publication under the same name in Computer Security Foundations (CSF) 201

Clustering of Curve Types using Similarity Scores

Curves of trends of content interaction events (e.g., views, shares, likes, etc.) versus time are of interest to social media and content-sharing services. Clustering trends can be used to classify, profile, and understand content creators or influencers. Clustering can also be used to recognize abusers, e.g., users that attempt to generate fraudulent views or likes in an effort to boost advertising revenue. This disclosure describes techniques to define similarity functions, or equivalently, distance measures, to enable the clustering of trends into trend types

Why healthcare workers are sick of TB.

Dr Thato Mosidi never expected to be diagnosed with tuberculosis (TB), despite widely prevalent exposure and very limited infection control measures. The life-threatening diagnosis of primary extensively drug-resistant TB (XDR-TB) came as an even greater shock. The inconvenient truth is that, rather than being protected, Dr Mosidi and thousands of her healthcare colleagues are at an increased risk of TB and especially drug-resistant TB. In this viewpoint paper we debunk the widely held false belief that healthcare workers are somehow immune to TB disease (TB-proof) and explore some of the key factors contributing to the pervasive stigmatization and subsequent non-disclosure of occupational TB. Our front-line workers are some of the first to suffer the consequences of a progressively more resistant and fatal TB epidemic, and urgent interventions are needed to ensure the safety and continued availability of these precious healthcare resources. These include the rapid development and scale-up of improved diagnostic and treatment options, strengthened infection control measures, and focused interventions to tackle stigma and discrimination in all its forms. We call our colleagues to action to protect themselves and those they care for

Agents of change: The role of healthcare workers in the prevention of nosocomial and occupational tuberculosis.

Healthcare workers (HCWs) play a central role in global tuberculosis (TB) elimination efforts but their contributions are undermined by occupational TB. HCWs have higher rates of latent and active TB than the general population due to persistent occupational TB exposure, particularly in settings where there is a high prevalence of undiagnosed TB in healthcare facilities and TB infection control (TB-IC) programmes are absent or poorly implemented. Occupational health programmes in high TB burden settings are often weak or non-existent and thus data that record the extent of the increased risk of occupational TB globally are scarce. HCWs represent a limited resource in high TB burden settings and occupational TB can lead to workforce attrition. Stigma plays a role in delayed diagnosis, poor treatment outcomes and impaired well-being in HCWs who develop TB. Ensuring the prioritization and implementation of TB-IC interventions and occupational health programmes, which include robust monitoring and evaluation, is critical to reduce nosocomial TB transmission to patients and HCWs. The provision of preventive therapy for HCWs with latent TB infection (LTBI) can also prevent progression to active TB. Unlike other patient groups, HCWs are in a unique position to serve as agents of change to raise awareness, advocate for necessary resource allocation and implement TB-IC interventions, with appropriate support from dedicated TB-IC officers at the facility and national TB programme level. Students and community health workers (CHWs) must be engaged and involved in these efforts. Nosocomial TB transmission is an urgent public health problem and adopting rights-based approaches can be helpful. However, these efforts cannot succeed without increased political will, supportive legal frameworks and financial investments to support HCWs in efforts to decrease TB transmission

Why healthcare workers are sick of TB

Dr Thato Mosidi never expected to be diagnosed with tuberculosis (TB), despite widely prevalent exposure and very limited infection control measures. The life-threatening diagnosis of primary extensively drug-resistant TB (XDR-TB) came as an even greater shock. The inconvenient truth is that, rather than being protected, Dr Mosidi and thousands of her healthcare colleagues are at an increased risk of TB and especially drug-resistant TB. In this viewpoint paper we debunk the widely held false belief that healthcare workers are somehow immune to TB disease (TB-proof) and explore some of the key factors contributing to the pervasive stigmatization and subsequent non-disclosure of occupational TB. Our front-line workers are some of the first to suffer the consequences of a progressively more resistant and fatal TB epidemic, and urgent interventions are needed to ensure the safety and continued availability of these precious healthcare resources. These include the rapid development and scale-up of improved diagnostic and treatment options, strengthened infection control measures, and focused interventions to tackle stigma and discrimination in all its forms. We call our colleagues to action to protect themselves and those they care for

A Policy Semantics and a Programming Language for Securing Software

The work presented in this thesis contributes to the information flowpolicy specification language Paralocks and the enforcement of Paralockspolicies in the programming language Paragon.The thesis starts with a programming tutorial on Paragon. The tutorialaims to make Paragon accessible for programmers without any familiaritywith information flow theory. We gradually introduce the Java programmerto various information flow concepts using the Paragon programming lan-guage. The tutorial also provides information and design patterns needed toset up realistic software applications in Paragon.Next we focus our attention on the design and implementation of Paragon.We discuss how the Paralocks language is generalised to integrate moretightly with Java’s object-oriented programming style, on which Paragonis built. Combined with the dynamic nature of Paralocks policies, Paragonpromises to be a flexible and expressive programming language.Finally we present an alternative semantics for Paralocks, based on thedeclarative language Datalog. Compared to Paralocks’ original semantics,the Datalog-inspired semantics provides a more natural and intuitive inter-pretation for Paralocks policies. We show that the new semantics coincideswith the original semantics. It also allows us to adopt Datalog extensionsand algorithms into Paralocks and Paragon

Protecting Information under Dynamic Policies: Specification, Conditions and Enforcement

Information-flow control enforces security policies on the information handled by computer applications. These policies often contain dynamic aspects, specifying how the confidentiality and integrity of information changes over time. This thesis focuses on the enforcement of such dynamic policies. The contributions are divided into three parts. Firstly, we need a means to specify our dynamic concerns in a manner that can be understood by a computer. The thesis builds on the Paralocks language as a suitable specification mechanism for such dynamic policies. Secondly, having specified a dynamic policy we require an understanding of what it means for a program to comply with that policy. The thesis identifies and addresses several of the challenges that the dynamic nature of policies introduces. Finally, given a policy specification and a definition of policy compliance, we explore how we can mechanically verify this compliance on programs. The thesis discusses two approaches: one static, using a type system, and one dynamic, using a run-time monitor

Dynamic enforcement of dynamic policies

LIO is a dynamic information-flow control system embedded in Haskell that uses a runtime monitor to enforce noninterference. The monitor is written as a library, requiring no changes to the runtime. We propose to extend LIO with a state component, allowing us to enforce not only noninterference but also information-flow policies that change while the program is running

Dynamic Enforcement of Dynamic Policies

This paper presents SLIO, an information-flow control mechanism enforcing dynamic policies: security policies which change the relation between security levels while the system is running. SLIO builds on LIO, a floating-label information-flow control system embedded in Haskell that uses a runtime monitor to enforce security. We identify an implicit flow arising from the decision to change the policy based on sensitive information and introduce a corresponding check in the enforcement mechanism. We provide a formal security guarantee for SLIO, presented as a knowledge-based property, which specifies that observers can only learn information in accordance with the level ordering. Like LIO, SLIO is a generic enforcement mechanism, parametrised on the concrete instantiation of security labels and their policy change mechanism. To illustrate the applicability of our results, we implement well-known label models such as DLM, the Flowlocks framework, and DC labels in SLIO