WAF-A-MoLE: An adversarial tool for assessing ML-based WAFs

Abstract Web Application Firewalls (WAFs) are plug-and-play security gateways that promise to enhance the security of a (potentially vulnerable) system with minimal cost and configuration. In recent years, machine learning-based WAFs are catching up with traditional, signature-based ones. They are competitive because they do not require predefined rules; instead, they infer their rules through a learning process. In this paper, we present WAF-A-MoLE, a WAF breaching tool. It uses guided mutational-based fuzzing to generate adversarial examples. The main applications include WAF ( i ) penetration testing, ( i i ) benchmarking and ( i i i ) hardening

On the stability of metal nanoparticles synthesized by laser ablation in liquids

Nanoparticles (NPs) synthesized through chemical routes are stabilized by a surface layer of capping agents. These molecules, beside avoid the infinite growth of the solid phase, impart steric or electrostatic repulsive inter- particle interactions. The technique known as “Laser ablation in liquid” (LAL) is an alternative technique to synthesize capping agents-free metal nanoparticles.1 LAL involves focused laser pulsed irradiation of a bulk metal target in a liquid and consist of four stages . Laser-matter interaction, plasma induction, cavitation bubble formation and particle release in solution. Strikingly, LAL leads to the formation of very stable “naked” NPs that are long standing for months. It is worth emphasizing that the stabilization of noble metal colloids in water is challenging because of the large Hamaker constant. Noble metal NPs prepared by LAL have a large negative zeta-potential and therefore their stability should be electrostatic in nature and it is due to the presence negative surface charges. The question is what is the origin of these surface charges? Common explanations for this phenomenon involve the presence of gold oxides and/or the anion adsorption.2, 3 However, the presence of oxidized gold species on the surface of NPs prepared in water has been recently questioned on the basis of XPS analysis.4 Very recently we have accumulated evidences that, in the case of gold NPs prepared by LAL, the metal oxidation and anion adsorptions have only a minor role on building the negative surface potential and we proposed that excess electrons formed within the plasma phase could charge the gold particles.5 The figure below describes an experiment that points in this direction: the addition of macroscopic metallic objects induce the loss of charge (as seen in the temporal evolution of the zeta-potential) and eventually NPs aggregation pnly the case of gold NP synthesized by LAL while it is ineffective in the case of NP synthesized by the classical Turkevitch chemical reduction of HAuCl4 reduction (see the picture of the cuvettes after 4 days). Please click Additional Files below to see the full abstract

Lactate as a marker of energy failure in critically ill patients: hypothesis

Lactate measurement in the critically ill has been traditionally used to stratify patients with poor outcome. However, plasma lactate levels are the result of a finely tuned interplay of factors that affect the balance between its production and its clearance. When the oxygen supply does not match its consumption, organisms such as man who are forced to produce ATP for their integrity adapt in many different ways up to the point when energy failure occurs. Lactate, being part of the adaptive response, may then be used to assess the severity of the supply/demand imbalance. In such a scenario, the time to intervention becomes relevant: early and effective treatment may allow the cell to revert to a normal state, as long as the oxygen machinery (i.e. mithocondria) is intact. Conversely, once the mithocondria are deranged, energy failure occurs even in the presence of normoxia. The lactate increase in critically ill patients may therefore be viewed as an early marker of a potentially reversible state

Preoperative SARS-CoV-2 infection screening before thoracic surgery during COVID-19 pandemic: a multicenter retrospective study

Objectives. During coronavirus disease (COVID-19) pandemic, preoperative screening before thoracic surgery is paramount in order to protect patients and staff from undetected infections. This study aimed to determine which preoperative COVID-19 screening tool was the most effective strategy before thoracic surgery. Methods. This retrospective cohort multicenter study was performed at 3 Italian thoracic surgery centers. All adult patients scheduled for thoracic surgery procedures from 4th March until 24th April, 2020, and submitted to COVID-19 preoperative screenings were included. The primary outcome was the yield of screening of the different strategies. Results. A total of 430 screenings were performed on 275 patients; 275 anamnestic questionnaires were administered. 77 patients were screened by an anamnestic questionnaire and reverse transcriptase polymerase chain reaction (RT-PCR). 78 patients were selected to combine screening with anamnestic questionnaire and chest computed tomography (CT). The positive yield of screening using a combination of anamnestic questionnaire and RT-PCR was 7.8% (95% CI: 2.6-14.3), while using a combination of anamnestic questionnaire and chest CT was 3.8% (95% CI: 0-9). Individual yields were 1.1% (95% CI: 0-2.5) for anamnestic questionnaire, 5.2% (95% CI: 1.3-11.7) for RT-PCR, and 3.8% (95% CI: 0-9). Conclusions. The association of anamnestic questionnaire and RT-PCR is able to detect around 8 positives in 100 asymptomatic patients. This combined strategy could be a valuable preoperative SARS-CoV-2 screening tool before thoracic surgery

On the stability of gold nanoparticles synthesized by laser ablation in liquids

“Naked” gold nanoparticles (AuNPs), synthesized in the absence of any capping agents, prepared by pulsed laser ablation in liquid (PLAL) are stabilized by negative charges. Common explanations for this phenomenon involve the presence of gold oxides and/or the anion adsorption. We have found that AuNP ablated in solutions of acids with very different oxidation power, viz. HCl, H2SO4, HNO3 share the same size and ζ-potential. Although, gold oxides have pKas ≈ 4, the ζ-potential of AuNPs ablated in solutions with pH ⩽ 4 is always negative. These evidences suggest that the gold oxidation and anion adsorptions have only a minor role on building the negative surface potential and we hypothesize, for the first time, that excess electrons formed within the plasma phase could charge the metallic particles. In our model, a crucial point is that the colloidal size of the NP maintains the energy of the electrons small enough to preclude chemical reactions but with a surface potential yet large enough to stabilize the AuNPs with respect to aggregation. A confirmation of the hypothesis of “electron-stabilized nanoparticles” is that either the addition of macroscopic metallic objects either the contact with a “grounded” copper wire induce the loss of charge and AuNPs aggregation

Nanoparticle Enhanced Laser-Induced Breakdown Spectroscopy for Microdrop Analysis at subppm Level

In this paper, nanoparticle enhanced laser-induced breakdown spectroscopy (NELIBS) was applied to the elemental chemical analysis of microdrops of solutions with analyte concentration at subppm level. The effect on laser ablation of the strong local enhancement of the electromagnetic field allows enhancing the optical emission signal up to more than 1 order of magnitude, enabling LIBS to quantify ppb concentration and notably decreasing the limit of detection (LOD) of the technique. At optimized conditions, it was demonstrated that NELIBS can reach an absolute LOD of few picograms for Pb and 0.2 pg for Ag. The effect of field enhancement in NELIBS was tested on biological solutions such as protein solutions and human serum, in order to improve the sensitivity of LIBS with samples where the formation and excitation of the plasma are not as efficient as with metals. Even in these difficult cases, a significant improvement with respect to conventional LIBS was observed

Perspective on the use of nanoparticles to improve LIBS analytical performance: nanoparticle enhanced laser induced breakdown spectroscopy (NELIBS)

In this paper, the new approach for Laser Induced Breakdown Spectroscopy (LIBS) based on nanoparticle deposition on the sample surface is reviewed from both fundamental and application points of view. The case of Nanoparticle-Enhanced LIBS (NELIBS) of metal samples is used for describing and discussing the main causes of the emission signal enhancement. A set of test cases is presented, which shows enhancements up to 1–2 orders of magnitude obtained using NELIBS with respect to LIBS. The feasibility and potential of NELIBS are also discussed for several analytical applications, including analysis of metallic samples, transparent samples and aqueous solution

Study of the Effect of Water Pressure on Plasma and Cavitation Bubble Induced by Pulsed Laser Ablation in Liquid of Silver and Missed Variations of Observable Nanoparticle Features

In this work the effects of the pressure between 1–150 Bar on pulsed laser ablation in liquids (PLAL) during the production of silver nanoparticles (AgNPs) in water was investigated. The produced NPs are the results of two different well-known stages which are the plasma and the bubble evolution occurring until the generated material is released into the solution. The main aim of this work is to show which roles is played by the variation of water pressure on the laser induced plasma and the cavitation bubble dynamics during the NPs formation. Their implication on the comprehension of the as-produced NPs formation mechanisms is treated. The typical timescales of the different stages occurring in water at different pressures have been studied by optical emission spectroscopy (OES), imaging and shadowgraph experiments. Finally surface plasmon resonance (SPR) spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS) and scanning electron microscopy (SEM) for characterization of the material released in solution, have been used