Understanding the Practices of Global Censorship through Accurate, End-to-End Measurements

2021 ◽  
Vol 5 (3) ◽  
pp. 1-25
Author(s):  
Lin Jin ◽  
Shuai Hao ◽  
Haining Wang ◽  
Chase Cotton
Keyword(s):  
Large Scale ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Ground Truth ◽  
Positive Rate ◽  
End To End ◽  
Internet Censorship ◽  
Different Response ◽  
Vantage Points

It is challenging to conduct a large scale Internet censorship measurement, as it involves triggering censors through artificial requests and identifying abnormalities from corresponding responses. Due to the lack of ground truth on the expected responses from legitimate services, previous studies typically require a heavy, unscalable manual inspection to identify false positives while still leaving false negatives undetected. In this paper, we propose Disguiser, a novel framework that enables end-to-end measurement to accurately detect the censorship activities and reveal the censor deployment without manual efforts. The core of Disguiser is a control server that replies with a static payload to provide the ground truth of server responses. As such, we send requests from various types of vantage points across the world to our control server, and the censorship activities can be recognized if a vantage point receives a different response. In particular, we design and conduct a cache test to pre-exclude the vantage points that could be interfered by cache proxies along the network path. Then we perform application traceroute towards our control server to explore censors' behaviors and their deployment. With Disguiser, we conduct 58 million measurements from vantage points in 177 countries. We observe 292 thousand censorship activities that block DNS, HTTP, or HTTPS requests inside 122 countries, achieving a 10^-6 false positive rate and zero false negative rate. Furthermore, Disguiser reveals the censor deployment in 13 countries.

scholarly journals A Single Sided Edge Marking Method for Detecting Pectoral Muscle in Digital Mammograms

2018 ◽  
Vol 8 (1) ◽  
pp. 2367-2373 ◽  
Author(s):  
G. Toz ◽  
P. Erdogmus
Keyword(s):  
Breast Cancer ◽  
False Positive ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Ground Truth ◽  
Pectoral Muscle ◽  
Computer Assisted ◽  
Positive Rate ◽  
Assisted Diagnosis

In the computer-assisted diagnosis of breast cancer, the removal of pectoral muscle from mammograms is very important. In this study, a new method, called Single-Sided Edge Marking (SSEM) technique, is proposed for the identification of the pectoral muscle border from mammograms. 60 mammograms from the INbreast database were used to test the proposed method. The results obtained were compared for False Positive Rate, False Negative Rate, and Sensitivity using the ground truth values pre-determined by radiologists for the same images. Accordingly, it has been shown that the proposed method can detect the pectoral muscle border with an average of 95.6% sensitivity.

Letters to the Editor

PEDIATRICS ◽  
1981 ◽  
Vol 68 (1) ◽  
pp. 144-145
Author(s):  
Lachlan Ch De Crespigny ◽  
Hugh P. Robinson
Keyword(s):  
Real Time ◽  
Linear Array ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Letters To The Editor ◽  
Premature Babies ◽  
Computed Tomography Scans ◽  
Positive Rate ◽  
Time Linear

We read with interest the report which suggested that the diagnosis of cerebroventricular hemorrhage ([CVH] including both subependymal [SEH] and intraventricular) with real time ultrasound was unreliable.1 Ultrasound, when compared with computed tomography scans, had a 35% false-positive rate and a 21% false-negative rate. In our institution over a 12-month period more than 200 premature babies have been examined (ADR real time linear array scanner with a 7-MHz transducer).

Pathologic Assessment of Computerized Tomography Accuracy for the Evaluation of the Laryngeal Cartilaginous Frame Work in Laryngopharyngeal Carcinomas

1989 ◽  
Vol 75 (2) ◽  
pp. 156-162 ◽  
Author(s):  
Sandro Sulfaro ◽  
Francesco Querin ◽  
Luigi Barzan ◽  
Mario Lutman ◽  
Roberto Comoretto ◽  
...  
Keyword(s):  
Computerized Tomography ◽  
False Positive ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Cartilage Destruction ◽  
High False Negative Rate ◽  
Positive Rate ◽  
Pathologic Assessment ◽  
Low Sensitivity

Sixty-six whole-organ sectioned laryngopharyngectomy specimens removed for cancer during a seven-year period were uniformly examined to determine the accuracy of preoperative high resolution computerized tomography (CT) for detection of cartilaginous involvement. Our results indicate that CT has a high overall specificity (88.2%) but a low sensitivity (47.1 %); we observed a high false-negative rate (26.5%) and a fairly low false-positive rate (5.9%). Massive cartilage destruction was easily assessed by CT, whereas both small macroscopic and microscopic neoplastic foci of cartilaginous invasion were missed on CT scans. Moreover, false-positive cases were mainly due to proximity of the tumor to the cartilage. Clinical implications of these results are discussed.

scholarly journals Macromolecule Particle Picking and Segmentation of a KLH Database by Unsupervised Cryo-EM Image Processing

Biomolecules ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 809
Author(s):  
Miguel Carrasco ◽  
Patricio Toledo ◽  
Nicole D. Tischler
Keyword(s):  
Signal To Noise Ratio ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Keyhole Limpet Hemocyanin ◽  
True Positive Rate ◽  
Cryo Electron Microscopy ◽  
Positive Rate ◽  
Top View ◽  
Non Negative Matrix Factorization

Segmentation is one of the most important stages in the 3D reconstruction of macromolecule structures in cryo-electron microscopy. Due to the variability of macromolecules and the low signal-to-noise ratio of the structures present, there is no generally satisfactory solution to this process. This work proposes a new unsupervised particle picking and segmentation algorithm based on the composition of two well-known image filters: Anisotropic (Perona–Malik) diffusion and non-negative matrix factorization. This study focused on keyhole limpet hemocyanin (KLH) macromolecules which offer both a top view and a side view. Our proposal was able to detect both types of views and separate them automatically. In our experiments, we used 30 images from the KLH dataset of 680 positive classified regions. The true positive rate was 95.1% for top views and 77.8% for side views. The false negative rate was 14.3%. Although the false positive rate was high at 21.8%, it can be lowered with a supervised classification technique.

Validity and Reliability of the Hooper Visual Organization Test

1974 ◽  
Vol 39 (1) ◽  
pp. 95-100 ◽  
Author(s):  
Allan Gerson
Keyword(s):  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Functional Disorders ◽  
Validity And Reliability ◽  
Clinical Value ◽  
Clear Cut ◽  
Positive Rate ◽  
Organic Brain ◽  
Visual Organization

To assess the validity and reliability of the Hooper Visual Organization Test, 68 Ss, of whom 16 were clinically and psychometrically determined to be suffering from organic brain damage, 19 had functional disorders, and 33 were without organic or functional disorders (normal), were given the test. The instrument was shown to be reliable ( r = .80), however, clear-cut discriminations between groups were not achieved. There were significant differences in scores of normal and damaged groups, functional and damaged Ss, but not functional and normal Ss. The qualitative signs said to aid in differentiations were totally absent from all protocols. Performance was affected in part by IQ and other aspects of recognition of meaning. There was a 19% false negative rate for the functionals and a 51% false positive rate for normals. The conclusion was that this device is of dubious clinical value.

Empirical mean curve decomposition with multiwavelet transformation for eye movements recognition using electrooculogram signals

2020 ◽  
Vol 234 (8) ◽  
pp. 794-811
Author(s):  
Harikrishna Mulam ◽  
Malini Mudigonda
Keyword(s):  
Neural Network ◽  
Eye Movements ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Principal Component ◽  
The Neural Network ◽  
Marquardt Algorithm ◽  
Positive Rate ◽  
Sensitivity Specificity

Many research works are in progress in classification of the eye movements using the electrooculography signals and employing them to control the human–computer interface systems. This article introduces a new model for recognizing various eye movements using electrooculography signals with the help of empirical mean curve decomposition and multiwavelet transformation. Furthermore, this article also adopts a principal component analysis algorithm to reduce the dimension of electrooculography signals. Accordingly, the dimensionally reduced decomposed signal is provided to the neural network classifier for classifying the electrooculography signals, along with this, the weight of the neural network is fine-tuned with the assistance of the Levenberg–Marquardt algorithm. Finally, the proposed method is compared with the existing methods and it is observed that the proposed methodology gives the better performance in correspondence with accuracy, sensitivity, specificity, precision, false positive rate, false negative rate, negative predictive value, false discovery rate, F1 score, and Mathews correlation coefficient.

scholarly journals Malicious Domain Names Detection Algorithm Based on N-Gram

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Hong Zhao ◽  
Zhaobin Chang ◽  
Guangbin Bao ◽  
Xiangyan Zeng
Keyword(s):  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Detection Algorithm ◽  
Internet Security ◽  
Domain Name ◽  
Domain Names ◽  
Malicious Attack ◽  
Positive Rate ◽  
N Gram

Malicious domain name attacks have become a serious issue for Internet security. In this study, a malicious domain names detection algorithm based on N-Gram is proposed. The top 100,000 domain names in Alexa 2013 are used in the N-Gram method. Each domain name excluding the top-level domain is segmented into substrings according to its domain level with the lengths of 3, 4, 5, 6, and 7. The substring set of the 100,000 domain names is established, and the weight value of a substring is calculated according to its occurrence number in the substring set. To detect a malicious attack, the domain name is also segmented by the N-Gram method and its reputation value is calculated based on the weight values of its substrings. Finally, the judgment of whether the domain name is malicious is made by thresholding. In the experiments on Alexa 2017 and Malware domain list, the proposed detection algorithm yielded an accuracy rate of 94.04%, a false negative rate of 7.42%, and a false positive rate of 6.14%. The time complexity is lower than other popular malicious domain names detection algorithms.

Correlation of preoperative citology/histology in radiologically detected lesions and histologic findings at excision

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 1552-1552
Author(s):  
P. Manente ◽  
G. Vicario ◽  
E. Scelzi ◽  
L. Sartor ◽  
L. Nicolardi ◽  
...  
Keyword(s):  
High Performance ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Needle Aspiration ◽  
European Guidelines ◽  
Breast Abnormality ◽  
Positive Rate ◽  
Preoperative Procedures ◽  
Screening Assessment

1552 Background: The major techniques used to diagnose breast abnormality has been for many years fine-needle aspiration (FNA) cytology and core needle biopsy (CNB) and more recently vacuum-assisted core biopsy (VACB). These techniques are accurate and allow definitive therapeutic surgery. The aim of our study was to detemine whether cytology/histologic findings mach histologic findings at excision. Methods: In our Institution, between January 2004 and June 2006, 43,138 mammographic exams were performed. 1,012 patients had patological lesions at mammography: 617 FNA cytology ( C due to European guidelines for breast cancer screening assessment) and 395 CNB/VACB (B) were performed. Patients with respectively suspicious and malignant FNA cytology (C4 and C5) and respectively uncertain malignant potential, suspicious and malignant histology (B3, B4 and B5) underwent to surgery. Results: The number of cancer identified by FNA cytology was 158 and the number of cancer identified by CNB/VACB was 253. The correlation of preoparative citology/histology with definitive histology had showed: false negative rate respectively 0.79% for histology (B) and 3.16% for cytology (C). False positive rate was respectively 0.4% for B and 0.63 for C. Complete sensitivity was 98.2% for B and 89.87% for C. Absolute sensitivity was 90.51% for B and 76.58% for C. Conclusions: Our data demostrated very high performance of diagnostic preoperative procedures due to multidisciplinary approach between the radiologists, the clinicians and the pathologists. No significant financial relationships to disclose.

Comparison of the BAX System PCR Method to Brazil's Official Method for the Detection of Salmonella in Food, Water, and Environmental Samples

2008 ◽  
Vol 71 (12) ◽  
pp. 2442-2447 ◽  
Author(s):  
INGRID BOESCHE TOMAZELLI ◽  
JOSINETE BARROS de FREITAS ◽  
LEANIA MARIA FABBI ◽  
TEREZINHA AGNESE FILIPINI ◽  
CLÁUDIA MARIA da SILVA ◽  
...  
Keyword(s):  
Environmental Samples ◽  
Limit Of Detection ◽  
False Positive Rate ◽  
False Negative ◽  
False Negative Rate ◽  
Reference Method ◽  
Culture Method ◽  
Official Method ◽  
Positive Rate ◽  
Pcr Method

A two-stage study compared the BAX system PCR method with the reference culture method used by the Brazilian Ministry of Agriculture and Food Supply for the detection of Salmonella in food, water, and environmental samples. In stage 1, fish matrix samples (n = 258) were spiked at several levels with Salmonella and a combination of Salmonella and non-Salmonella competitive organisms. Replicates were analyzed by the BAX system PCR method and the reference method with comparable results (sensitivity ≥ 97.5%, specificity ≥ 83.3%) from both methods at the limit of detection. In stage 2, a total of 1,988 samples with 70 product types were analyzed with both methods. Five laboratories were involved in this study, and the samples used were from routine analyses. The BAX system PCR method was shown to be comparable to the reference method, with a limit of detection of 1.0 to 2.0 CFU/25 g of sample. Analysis of the results obtained in stage 2 and in the combination of stages 1 and 2 for the BAX system showed the following performance: sensitivity ≥ 99.0%, specificity ≥ 97.2%, false-negative rate ≤ 1.1%, and false-positive rate ≤ 2.8%. Therefore, the BAX system appears to be equivalent to the reference method, with ≥ 97.3% agreement.

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