QA Official

Firewall Series (II)-Packet Filtering, Firewall's Main Technology, State Detection Technology

https://qaofficial.com/post/2019/04/10/69901-firewall-series-ii-packet-filtering-firewallamp#x27s-main-technology-state-detection-technology.html 2019-04-10
Firewall Series (II)-Main Technologies of Firewall Essential Knowledge: TCP/IP Basis Packet Filtering work object–> packetFirewall processes packets before they enter the systemThe Firewall module that implements Packet Filtering should be located at the network layer of the operating system protocol stack. Filter Objects filtering for IP View the packet header of each IP packet, compare the packet header data with the rule set, forward the packets allowed by the rule set, and reject the packets not allowed by the rule set

Firewall Series (III)-Agent Technology for Firewall's Main Technologies

https://qaofficial.com/post/2019/04/10/69895-firewall-series-iii-agent-technology-for-firewallamp#x27s-main-technologies.html 2019-04-10
Firewall Series (III)-Main Technologies of Firewall Proxy Technology Proxy Technology Overview The Firewall of proxy technology runs between the internal network and the external network in the form of a proxy server, realizes the security control function at the application layer, and plays the role of transferring application services between the internal network and the external network. 1. Agent Execution Process (Two Cases) 1. The proxy server monitors the request

Firewall Technology (I)

https://qaofficial.com/post/2019/04/10/69890-firewall-technology-i.html 2019-04-10
Firewall Technology (I) At present, effective measures to ensure network security mainly include: Firewall, identity authentication, encryption, digital signature and content check, etc. Firewall refers to the combination of a series of components arranged between different networks or network security domains.It is the only entrance and exit of information between different networks or network security domains. It can control (allow, deny and monitor) the flow of information into and out of the network according to the enterprise's security policies and has strong anti-attack capability.

Firewall Type Summary

https://qaofficial.com/post/2019/04/10/69899-firewall-type-summary.html 2019-04-10
PS: Although the annotation in this article is original, it is basically an excerpt from the book content, so it cannot be regarded as original completely. It is only the author's knowledge note. This is a summary of the list in the book CCNP Security Firewall 642-618 Official Certificate Guide. In addition to referring to this book, we also refer to the contents of Network Secretity Principles and Practices and CCNA Security Official Certificate Guide as well.

Introduction to Information Security Knowledge Points

https://qaofficial.com/post/2019/04/10/69892-introduction-to-information-security-knowledge-points.html 2019-04-10
Introduction to Information Security Knowledge Points 1. Cognitive psychology 1. Information security: Information security refers to the protection of the hardware, software and data in the information network system from accidental or malicious causes, such as damage, alteration, leakage, continuous and reliable operation of the system and uninterrupted information service. 2. Security vulnerability: refers to a certain attribute of a computer system that may be maliciously exploited by intruders.

Knowledge Point 8: Common Sorting Algorithms-Select Sorting

https://qaofficial.com/post/2019/04/10/69784-knowledge-point-8-common-sorting-algorithms-select-sorting.html 2019-04-10
Yesterday we have introduced the principle and implementation of fast sorting, and we have also supplemented the execution process of selective sorting through several cyclic and progressive assumptions.However, it is a pity that these blogs have not been written on my computer. They use the new linux system and have no java execution environment or Android development environment.So blogs about Android series will be updated at the weekend.All right, let's not say much, let's continue our selection sorting algorithm.

Matrix Connotation!It is helpful for the physical meaning of inverse matrix!

https://qaofficial.com/post/2019/04/10/69861-matrix-connotationit-is-helpful-for-the-physical-meaning-of-inverse-matrix.html 2019-04-10
If you are not familiar with the concept of linear algebra and want to study natural science, it now looks like illiteracy.However, "according to the current international standards, linear algebra is expressed through axiomatization. it is the second generation of mathematical models, which brings difficulties in teaching."* What exactly is a matrix?Vectors can be considered as representations of objects with n mutually independent properties (dimensions). What is a matrix?If we think that a matrix is an expansion of a new composite vector composed of a set of column (row) vectors, then why is this expansion so widely used?

Meng Yan BLOG Understanding Matrix One, Two, Three

https://qaofficial.com/post/2019/04/10/69845-meng-yan-blog-understanding-matrix-one-two-three.html 2019-04-10
Not long ago chensh wanted to act as a teacher and teach others linear algebra for ulterior purposes.Therefore, I was seized and discussed with him several times on some issues of falsity in linear algebra.Obviously, chensh felt that it was still relatively difficult for him not to be considered insane by that strong student when he was speaking linear algebra. Poor chensh, who let you go to this minefield?!Color makes one faint!

Selection Sorting of Nine Sorting Algorithms (Principle and Implementation)

https://qaofficial.com/post/2019/04/10/69756-selection-sorting-of-nine-sorting-algorithms-principle-and-implementation.html 2019-04-10
1. Algorithm idea: Select sorting, scan the sequence from beginning to end, find the smallest element, exchange with the first element, and then continue this selection and exchange method from the remaining elements to finally obtain an ordered sequence. 2, algorithm process Take a chestnut (the sorting process of the first trip) Original sequence: 49, 38, 65, 97, 76, 13, 27, 49 1) In the process of selecting and sorting,

Several Ways to Realize Thread Synchronization

https://qaofficial.com/post/2019/04/10/69814-several-ways-to-realize-thread-synchronization.html 2019-04-10
Why use synchronization? java allows multi-thread concurrent control. When multiple threads simultaneously operate a shareable resource variable (e.g. data addition, deletion, modification and check),This will lead to inaccurate data and conflicts between them. Therefore, a synchronization lock is added to avoid being called by other threads before the thread completes its operation.Therefore, the uniqueness and accuracy of the variable are guaranteed. synchronization method 1. Synchronization MethodThat is, there is a