Rethinking Pointer Reasoning in Symbolic Execution

Symbolic execution is a popular program analysis technique that allows seeking for bugs by reasoning over multiple alternative execution states at once. As the number of states to explore may grow exponentially, a symbolic executor may quickly run out of space. For instance, a memory access to a symbolic address may potentially reference the entire address space, leading to a combinatorial explosion of the possible resulting execution states. To cope with this issue, state-of-the-art executors concretize symbolic addresses that span memory intervals larger than some threshold. Unfortunately, this could result in missing interesting execution states, e.g., where a bug arises. In this paper we introduce MemSight, a new approach to symbolic memory that reduces the need for concretization, hence offering the opportunity for broader state explorations and more precise pointer reasoning. Rather than mapping address instances to data as previous tools do, our technique maps symbolic address expressions to data, maintaining the possible alternative states resulting from the memory referenced by a symbolic address in a compact, implicit form. A preliminary experimental investigation on prominent benchmarks from the DARPA Cyber Grand Challenge shows that MemSight enables the exploration of states unreachable by previous techniques

A Survey of Symbolic Execution Techniques

Many security and software testing applications require checking whether certain properties of a program hold for any possible usage scenario. For instance, a tool for identifying software vulnerabilities may need to rule out the existence of any backdoor to bypass a program's authentication. One approach would be to test the program using different, possibly random inputs. As the backdoor may only be hit for very specific program workloads, automated exploration of the space of possible inputs is of the essence. Symbolic execution provides an elegant solution to the problem, by systematically exploring many possible execution paths at the same time without necessarily requiring concrete inputs. Rather than taking on fully specified input values, the technique abstractly represents them as symbols, resorting to constraint solvers to construct actual instances that would cause property violations. Symbolic execution has been incubated in dozens of tools developed over the last four decades, leading to major practical breakthroughs in a number of prominent software reliability applications. The goal of this survey is to provide an overview of the main ideas, challenges, and solutions developed in the area, distilling them for a broad audience. The present survey has been accepted for publication at ACM Computing Surveys. If you are considering citing this survey, we would appreciate if you could use the following BibTeX entry: http://goo.gl/Hf5FvcComment: This is the authors pre-print copy. If you are considering citing this survey, we would appreciate if you could use the following BibTeX entry: http://goo.gl/Hf5Fv

Alcohol-specific activity in hospitals in England

Alcohol-related harm is placing increasing demands on the NHS. At a time when unprecedented efficiencies need to be made by the NHS and local authorities, preventative action must be taken seriously. This analysis explores trends in alcohol-specific activity in hospitals due to alcohol poisoning and alcohol-related inpatient admissions by looking at six years of hospital activity data in England. The analysis also explores the use of hospital services before and after a diagnosis of alcohol-related liver disease and highlights opportunities for preventative action to reduce future alcohol-related harm in England

Prevalencia y validez diagnóstica de los hallazgos de tomografía de tórax encontrados en pacientes con sospecha de tuberculosis pulmonar activa dentro de un área endémica

INTRODUCCIÓN: En Risaralda, departamento considerado zona endémica para la enfermedad, no se había efectuado ningún estudio que describiera la prevalencia de las imágenes de tomografía sugestivas de actividad tuberculosa ni que las relacionara con los resultados de cultivo. Se planteó un proyecto de investigación para generar información que permitiera modificar las prácticas actuales en cuanto al uso de este método diagnóstico en la caracterización de esta enfermedad tan prevalente y con alta mortalidad. MÉTODOS: Se diseñó un estudio de evaluación de la prueba diagnóstica, retrospectivo, observacional y descriptivo. Se recolectaron variables microbiológicas y radiológicas, a partir de registros de historia clínica e imágenes de tomografía de tórax, pertenecientes a pacientes hospitalizados con diagnóstico o sospecha de tuberculosis pulmonar activa, desde enero de 2014 hasta diciembre de 2017. Se construyó una tabla 2x2 para cada variable radiológica, en relación con el diagnóstico de la enfermedad dado por el cultivo; con lo que se calculó la sensibilidad, especificidad, valor predictivo positivo, valor predictivo negativo, razón de verosimilitud positiva y razón de verosimilitud negativa. Con la identificación de las variables de mejor desempeño se elaboró un análisis en paralelo. RESULTADOS: Se analizaron 628 registros de pacientes, en los que se hicieron 880 cultivos de especímenes respiratorios, la mayoría provenientes de Pereira. Se obtuvo cultivo en medio sólido para M. tuberculosis a partir de muestras de esputo (47%), lavado broncoalveolar (33,7%), aspirado traqueal (5,5%) y otras muestras como pleura y líquido pleural (13,8%). Los hallazgos de imagen más prevalentes fueron: derrame pleural libre (50,3%), consolidación (42%) y tractos fibróticos (33,5%), entre otros. El mejor desempeño diagnóstico lo tuvo la opacidad micronodular, árbol en gemación, cavitación apical y nódulo, cada uno con valor predictivo negativo mayor a 80%

Prevalence of anxiety, depression and post-traumatic stress disorder in the Kashmir Valley.

BACKGROUND: Following the partition of India in 1947, the Kashmir Valley has been subject to continual political insecurity and ongoing conflict, the region remains highly militarised. We conducted a representative cross-sectional population-based survey of adults to estimate the prevalence and predictors of anxiety, depression and post-traumatic stress disorder (PTSD) in the 10 districts of the Kashmir Valley. METHODS: Between October and December 2015, we interviewed 5519 out of 5600 invited participants, ≥18 years of age, randomly sampled using a probability proportional to size cluster sampling design. We estimated the prevalence of a probable psychological disorder using the Hopkins Symptom Checklist (HSCL-25) and the Harvard Trauma Questionnaire (HTQ-16). Both screening instruments had been culturally adapted and translated. Data were weighted to account for the sampling design and multivariate logistic regression analysis was conducted to identify risk factors for developing symptoms of psychological distress. FINDINGS: The estimated prevalence of mental distress in adults in the Kashmir Valley was 45% (95% CI 42.6 to 47.0). We identified 41% (95% CI 39.2 to 43.4) of adults with probable depression, 26% (95% CI 23.8 to 27.5) with probable anxiety and 19% (95% CI 17.5 to 21.2) with probable PTSD. The three disorders were associated with the following characteristics: being female, over 55 years of age, having had no formal education, living in a rural area and being widowed/divorced or separated. A dose-response association was found between the number of traumatic events experienced or witnessed and all three mental disorders. INTERPRETATION: The implementation of mental health awareness programmes, interventions aimed at high risk groups and addressing trauma-related symptoms from all causes are needed in the Kashmir Valley

Monitoring and Evaluating Psychosocial Intervention Outcomes in Humanitarian Aid.

Existing tools for evaluating psychosocial interventions (un-validated self-reporting questionnaires) are not ideal for use in non-Western conflict settings. We implement a generic method of treatment evaluation, using client and counsellor feedback, in 18 projects in non-Western humanitarian settings. We discuss our findings from the perspective of validity and suggestions for future research. A retrospective analysis is executed using data gathered from psychosocial projects. Clients (n = 7,058) complete two (complaints and functioning) rating scales each session and counsellors rate the client's status at exit. The client-completed pre- and post-intervention rating scales show substantial changes. Counsellor evaluation of the clients' status shows a similar trend in improvement. All three multivariable models for each separate scale have similar associations between the scales and the investigated variables despite different cultural settings. The validity is good. Limitations are: ratings give only a general impression and clinical risk factors are not measured. Potential ceiling effects may influence change of scales. The intra and inter-rater reliability of the counsellors' rating is not assessed. The focus on client and counsellor perspectives to evaluate treatment outcome seems a strong alternative for evaluation instruments frequently used in psychosocial programming. The session client rated scales helps client and counsellor to set mutual treatment objectives and reduce drop-out risk. Further research should test the scales against a cross-cultural valid gold standard to obtain insight into their clinical relevance

Accounting for False Positive HIV Tests: Is Visceral Leishmaniasis Responsible?

BACKGROUND: Co-infection with HIV and visceral leishmaniasis is an important consideration in treatment of either disease in endemic areas. Diagnosis of HIV in resource-limited settings relies on rapid diagnostic tests used together in an algorithm. A limitation of the HIV diagnostic algorithm is that it is vulnerable to falsely positive reactions due to cross reactivity. It has been postulated that visceral leishmaniasis (VL) infection can increase this risk of false positive HIV results. This cross sectional study compared the risk of false positive HIV results in VL patients with non-VL individuals. METHODOLOGY/PRINCIPAL FINDINGS: Participants were recruited from 2 sites in Ethiopia. The Ethiopian algorithm of a tiebreaker using 3 rapid diagnostic tests (RDTs) was used to test for HIV. The gold standard test was the Western Blot, with indeterminate results resolved by PCR testing. Every RDT screen positive individual was included for testing with the gold standard along with 10% of all negatives. The final analysis included 89 VL and 405 non-VL patients. HIV prevalence was found to be 12.8% (47/ 367) in the VL group compared to 7.9% (200/2526) in the non-VL group. The RDT algorithm in the VL group yielded 47 positives, 4 false positives, and 38 negatives. The same algorithm for those without VL had 200 positives, 14 false positives, and 191 negatives. Specificity and positive predictive value for the group with VL was less than the non-VL group; however, the difference was not found to be significant (p = 0.52 and p = 0.76, respectively). CONCLUSION: The test algorithm yielded a high number of HIV false positive results. However, we were unable to demonstrate a significant difference between groups with and without VL disease. This suggests that the presence of endemic visceral leishmaniasis alone cannot account for the high number of false positive HIV results in our study