• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.9
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• pp.3885-3906
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• 2020

Hybrid fuzzing which combines fuzzing and concolic execution, has proved its ability to achieve higher code coverage and therefore find more bugs. However, current hybrid fuzzers usually suffer from inefficiency and poor scalability when applied to complex, real-world program testing. We observed that the performance bottleneck is the inefficient cooperation between the fuzzer and concolic executor and the slow symbolic emulation. In this paper, we propose a novel solution named EPfuzzer to improve hybrid fuzzing. EPfuzzer implements two key ideas: 1) only the hardest-to-reach branch will be prioritized for concolic execution to avoid generating uninteresting inputs; and 2) only input bytes relevant to the target branch to be flipped will be symbolized to reduce the overhead of the symbolic emulation. With these optimizations, EPfuzzer can be efficiently targeted to the hardest-to-reach branch. We evaluated EPfuzzer with three sets of programs: five real-world applications and two popular benchmarks (LAVA-M and the Google Fuzzer Test Suite). The evaluation results showed that EPfuzzer was much more efficient and scalable than the state-of-the-art concolic execution engine (QSYM). EPfuzzer was able to find more bugs and achieve better code coverage. In addition, we discovered seven previously unknown security bugs in five real-world programs and reported them to the vendors.

• International Journal of Computer Science & Network Security
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• v.21 no.12
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• pp.207-212
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• 2021

A buffer overflow attack is carried out to subvert privileged program functions to gain control of the program and thus control the host. Buffer overflow attacks should be prevented by risk managers by eradicating and detecting them before the software is utilized. While calculating the size, correct variables should be chosen by risk managers in situations where fixed-length buffers are being used to avoid placing excess data that leads to the creation of an overflow. Metamorphism can also be used as it is capable of protecting data by attaining a reasonable resistance level [1]. In addition, risk management teams should ensure they access the latest updates for their application server products that support the internet infrastructure and the recent bug reports [2]. Scanners that can detect buffer overflows' flaws in their custom web applications and server products should be used by risk management teams to scan their websites. This paper presents an experiment of buffer overflow vulnerability and attack. The aims to study of a buffer overflow mechanism, types, and countermeasures. In addition, to comprehend the current detection plus prevention approaches that can be executed to prevent future attacks or mitigate the impacts of similar attacks.

• The Journal of the Korean Society for Microbiology
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• v.9 no.1
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• pp.7-11
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• 1974

The authors identified fifty-eight Shigella cultures among 1644 cultures and specimens of enteric pathogens collected from all over the country in 1973. Fifty-one out of fifty-eight cultures belonged to Shigella flexneri and the rest to Shigella sonnei. None of cultures belonging to either subgroup A or C was detected in 1973. Of fifty-one cultures of Shigella flexneri twenty-six cultures were $B_{2a}$, which were isolated in Seoul area and Kwangwon-Do. The rest were $B_{3a}$ which were isolated in Jeonla-bug-Do and Kangwon-Do. It would not be possible to understand that there might not have been the cases or carriers of Shigella in the areas where the organisms were not isolated in 1973 and that there might not have been any other serotypes existing in the country, although there was a quite disparity found in the distribution between different areas and in the detection of the serotypes as shown in Table 1. Concerning the biochemical properties there were only two cultures showing positive arginine decarboxylase test among $B_{2a}$, and there were three cultures of trehalose negative cultures, one of rhamnose positive culture and one of glycerol positive culture observed, which were considered to be unusual. All the Shigella cultures were sensitive to nitrofurantoin, cephalosporin and ampicillin, and resistant to colistin, bacitracin and neomycin. Majority of them showed sensitive results to gentamycin, and the majority of Shigella $B_{3a}$ appeared to be sensitive to chloramphenicol, tetracycline, oxytetracycline and doxycycline, but the majority of $B_{2a}$ and Shigella sonnei were observed resistant to those antibiotics by means of the In-Vitro tests.