Traditional Web database cache techniques have a major disadvantage, namely poor data freshness, because they employ an asynchronous data refresh strategy. A novel Web database cache, DB Facade, is proposed in this pa...
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Traditional Web database cache techniques have a major disadvantage, namely poor data freshness, because they employ an asynchronous data refresh strategy. A novel Web database cache, DB Facade, is proposed in this paper. DB Facade uses a main memory database to cache result sets of previous queries for subsequent reusing. Updates on backend database system are managed by delta tables, and then propagated to Web database cache in a near real-time manner, hence guarantee the freshness of data. DB Facade off loads query burden from backend database systems, and exploits the power of main memory database system to boost query performance. TPC-W testing result shows that the system's performance increases by about 17 percent.
The existing code injection attack defense methods have some deficiencies on performance overhead and effectiveness. In order to ensure the system performance, we propose a method that uses system call randomization t...
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ISBN:
(纸本)9781424442232
The existing code injection attack defense methods have some deficiencies on performance overhead and effectiveness. In order to ensure the system performance, we propose a method that uses system call randomization to counter code injection attacks based on instruction set randomization idea. An injected code would perform its actions with system calls. System call randomization on operating system level will prevent the injected code from executing correctly. Moreover, with an extended compiler, our method can perform source code randomization during compiling and implement binary executable files randomization by feature matching. The experiments show that our method can effectively counter variety code injection attacks with low overhead.
In recent years, Web sites have already become the attackers' main target. When attackers embed malicious code in the Web pages, they generally change the display mode of the corresponding HTML tags to make the di...
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In recent years, Web sites have already become the attackers' main target. When attackers embed malicious code in the Web pages, they generally change the display mode of the corresponding HTML tags to make the display effect of malicious code invisible or almost invisible to the browser users. In this paper, the concept of abnormal visibility is proposed to describe the display feature setting of malicious code embedded. According to the concept, a malicious code detection method based on abnormal visibility recognition is designed and a prototype system is implemented. Compared to traditional methods and systems, the method has higher efficiency and less maintenance cost. Besides, a special-purpose JavaScript interpreter is implemented to get the execution output of browser-end scripts that are often used to generate malicious code dynamically by attackers. Experiments show that this system can detect most of the malicious Web pages efficiently and at the same time locate the malicious code in the source code accurately.
Ranking is one of the key factors for efficient and effective XML information retrieval. Compared with traditional IR, XML information retrieval has introduced many new challenges, one of which is that the traditional...
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In this paper, a rapid resynchronization method using intent logs is suggested for replication in-memory databases supporting mobile communication applications. Both the identifiers of unsynchronized segments and the ...
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In this paper, a rapid resynchronization method using intent logs is suggested for replication in-memory databases supporting mobile communication applications. Both the identifiers of unsynchronized segments and the identifiers of the slaves who have missed the updates in the segments are recorded in the intent logs. When receiving a resynchronization request from a slave, the master will scan the intent logs to find the unsynchronized segments for the salve, and then send the segments gotten directly from its memory to the slave. The performance results shown the intent logs method can reduce resynchronization time than methods using transaction logs.
Web sites have become the main targets of many attackers. Signature-based detection needs to maintain a large signature database and Honeypot based methods are not efficient. Since attackers always make the malicious ...
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Web sites have become the main targets of many attackers. Signature-based detection needs to maintain a large signature database and Honeypot based methods are not efficient. Since attackers always make the malicious codes in Web pages difficult to detect by the browser users, their methods can be classified into various fingerprints. Various malicious codes were analyzed to identify 6 types of fingerprints. The system utilizes a spider integrated with script interpretation to fetch target Web pages and extract specific tags for detection by HTML parsing for matching with the fingerprints to detect malicious codes. This method needs fewer fingerprints than traditional detection methods and is more efficient. Results for 60 websites show that the system has a false negative rate of 2.63% and a false positive rate of 1.99%.
To support electronic commerce applications with high reliability requirements, a synchronous replication framework of database servers is designed in this paper. At first, a three-tier architecture consisting of Web ...
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Top-k queries in uncertain databases are quite popular and useful due to its wide application usage. However, compared to top-k in traditional databases, queries over uncertain database are more complicated because of...
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ISBN:
(纸本)9781424449934
Top-k queries in uncertain databases are quite popular and useful due to its wide application usage. However, compared to top-k in traditional databases, queries over uncertain database are more complicated because of the existence of exponential possible worlds. A Top-k aggregate query ranks groups of tuples by their aggregate values, sum or average for example, and returns k groups with the highest aggregate values. As a powerful semantic of top-k, global top-k, returns A highest-ranked tuples according to their probabilities of being in the top-k anTopswers in possible worlds. We propose a dynamic programming based method to process global top-k aggregate queries in uncertain database, where the number of retrieved tuples and group states generated on these tuples are minimized. Experiment results show that our algorithm is effective.
As one part of preprocessing, automatic word segmentation is an key issue in Chinese information retrieval. Since integral words are put wholly together to compose into the more meaningful words and more express users...
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The main problem of existing static vulnerability detection methods based source code analysis is their high false positive and false negative rates. One main reason is lack of accurate and effective identification an...
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The main problem of existing static vulnerability detection methods based source code analysis is their high false positive and false negative rates. One main reason is lack of accurate and effective identification and analysis of security-related program elements, e.g. data validation checking, tainted data source, etc. A static vulnerability detection method based on data security state tracing and checking is proposed. In this method, the state space of state machine model is extended;the security state of a variable is identified by a vector that may correspond to multiple security-related properties rather than by a single property;Fine-grained state transition is provided to support accurate recognition of program security-related behaviors;The recognition of validation checking is introduced in vulnerability state machine to reduce false positives;and a systematic discrimination mechanism for tainted data is constructed to prevent false negatives result from neglecting tainted data sources. The experimental results of a prototype system show that this method can effectively detect buffer overflow and other type's vulnerabilities in software systems, and with obviously lower false positive than existing mainstream static detection methods and avoid some serious false negatives of these methods.
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