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- How to solve Ulimit faults
- I encountered a very interesting problem recently. There is a group of HAProxy that has frequent problems. Log in to the server and check the CPU, memory, network, and IO. It was eventually discovered that there were more than 60,000 connections in the TIME_WAIT state on the machine. The TIME_WAIT state generally appears on proxy machines such as HAProxy and Nginx, mainly due to frequent active shutdowns. By modifying the reuse and recycling parameters, the problem can be solved relatively quickly. The statistics of network status can be calculated using the following command. netstat-ant|awk'/^tcp/{++S[$NF]}END{for(ainS
- Safety 1660 2023-05-16 15:39:09
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- What are the encryption algorithms commonly used on the web?
- Encryption algorithms can be divided into: reversible encryption and irreversible encryption, and reversible encryption can be divided into: symmetric encryption and asymmetric encryption. 1. Irreversible Encryption Common irreversible encryption algorithms include MD5, HMAC, SHA1, SHA-224, SHA-256, SHA-384, and SHA-512, among which SHA-224, SHA-256, SHA-384, and SHA-512 We can collectively call it the SHA2 encryption algorithm. The SHA encryption algorithm is more secure than MD5, and the SHA2 encryption algorithm is higher than SHA1. The number after SHA represents the length of the encrypted string. SHA1 will generate a 160-bit information digest by default. The most irreversible encryption algorithm
- Safety 1944 2023-05-16 14:43:12
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- What is the mastering procedure for 28BYJ-48 stepper motor?
- Although we have completed the program of using interrupts to control the rotation of the motor, in fact this program still has little practical value. We can't power it on and off every time we want it to rotate, right? Also, it must be able to not only rotate forward but also reverse, that is to say, it must not only be able to rotate around, but it must also be able to rotate back. Okay, let's make an example program. Combined with the key program in Chapter 8, we design a functional program like this: press the numeric keys 1 to 9 to control the motor to rotate 1 to 9 circles; use the up and down keys to change the rotation direction. , press the up key to rotate forward for 1 to 9 turns, and the down key to rotate in the reverse direction for 1 to 9 turns; the left key is fixed to rotate forward 90 degrees, and the right key is fixed to reverse 90 degrees; the Esc key terminates the transition. After this procedure, we can also further obtain
- Safety 968 2023-05-16 14:37:06
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- How to analyze BGP concepts
- Safety 772 2023-05-16 14:16:06
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- How to use JavaScript to implement screenshot function
- 1. The media type of the Blob must be "image/svg+xml" 2. A svg element is required 3. Insert a foreignObject element into the svg element 4. Put HTML that conforms to the specification into the foreignObject element and convert the dom to canvas. That's it. Simple, just a few steps above. The following is a simple demo given in the document: Documentvarcanvas=document.getElementById('canvas');varctx=canvas.getContext(&am
- Safety 2003 2023-05-16 14:07:06
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- How to implement switch WIFI configuration
- A relatively simple WiFi configuration I did recently was responsible for a firewall, a core switch, and a PoE switch. Neither AC nor AP are our responsibility. Let’s talk about the configuration of the firewall first: I won’t talk about the conventional deployment. G1/0/0 of the firewall is connected to the operator, set to the untrust zone, and configure the public IP address provided by the operator, 1.1.1.1G1/0/ 1 Connect to the core switch and set it to the trust zone. Configure the interconnection address security policy with the core switch: rulenametrustTOuntrustsource-zonetrustdestination-zoneuntrustsource-addres
- Safety 1869 2023-05-16 13:58:06
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- How to conduct mobile app security assessment and detection technology analysis
- Due to the increasingly developed network technology today, there are also many hidden dangers in the security of Android APPs, which require our constant attention to improve their security. Based on the security of system programs, system data, basic services, and application vulnerabilities, people continue to improve and form a more secure, stable, and complete mobile APP monitoring system to ensure the security of mobile APPs. It will serve as the primary line of defense for "malicious harm", that is, the first line of defense. This will also increase researchers' consideration of APP security assessment when developing mobile APPs, and help mobile APPs develop better and safer. The key points of protection for the new version of mobile app level protection evaluation are based on the latest level protection mobile Internet security extension standards.
- Safety 1486 2023-05-16 13:52:06
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- How to analyze Google Chrome remote code execution 0Day vulnerability notification
- 1. Overview On April 13, 2021, Antiy CERT discovered that foreign security researchers released a PoC of a remote code execution 0Day vulnerability in the Google Chrome browser. Attackers can use the vulnerability to construct a specially crafted page, and users accessing the page will cause remote code execution. The vulnerability affects the latest official version of Chrome (89.0.4389.114) and all earlier versions. Antiy CERT followed up and found out that due to the high usage rate of Google Chrome browser in China, this vulnerability has the risk of being exploited by malicious code and spread widely, and the threat level is high. At the same time, Antiy's CERT test found that some other domestic browsers using the Google Chrome kernel are also affected. Currently as
- Safety 935 2023-05-16 12:37:06
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- How to analyze DataSet objects and use them
- The concept of DataSet object: DataSet object can be regarded as a (Catch), which can retain the data found in the database, and can even temporarily store the entire database. DataSet is the representation of data in memory. DataSet object and data The connection to the source occurs very briefly. We disconnect from the data source immediately after obtaining the data. The connection will not be established until the data is modified or the data in the data source needs to be manipulated. The DataSet object contains a set of DataTable objects and DataRelation objects. DataTable object and use The DataTable object is one of the important objects of DataSet and represents a relational number in memory.
- Safety 1207 2023-05-16 11:55:06
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- What are the dangers of secondary release of C language source code?
- 1. Secondary release. A simple understanding of secondary release is that the memory pointed to by the same pointer is released twice. For C language source code, performing two free() operations on the same pointer may lead to a secondary release. Chapter 3.1 of this article The defect code is a description of such a situation. In the C++ language, improper shallow copy operation is one of the common causes of secondary release. For example: calling the assignment operator or copy constructor once will cause the data members of the two objects to point to the same dynamic memory. At this time, the reference counting mechanism becomes very important. When the reference counting is improper and an object goes out of scope, the destructor will release the memory shared by the two objects. The corresponding data member in another object will point to the memory address that has been released, and when this object
- Safety 2166 2023-05-16 11:37:11
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- Process analysis from entering the URL to the final browser rendering of the page content
- Prepare: When you enter a URL (such as www.coder.com) in the browser and hit Enter, the first thing the browser needs to do is to obtain the IP address of coder.com. The specific method is to send a UDP packet to DNS server, the DNS server will return the IP of coder.com. At this time, the browser will usually cache the IP address, so that the next visit will be faster. For example, in Chrome, you can view it through chrome://net-internals/#dns. With the server's IP, the browser can initiate an HTTP request, but the HTTPRequest/Response must be in the "virtual" TCP
- Safety 1575 2023-05-16 11:28:12
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- What are the weblogic attack techniques?
- Introduction: Weblogic servers are characterized by large and complex architectures, which are generally difficult for blue teams to defend and are mostly deployed on the external network. Moreover, weblogic's attack cost is relatively low. As long as there is a vulnerability, you can generally directly obtain the root permissions of the target server. During offensive and defensive exercises, it was focused on by all major attacking teams and defenders. Of course, there are more or less problems with various exploit programs currently available on the Internet, including my own tools. So recently, at the request of a friend, I sorted out some attack methods and "perfect" uses. The red team can use it to improve their own tools, and the blue team can use it to write traceability reports. 1. Detect whether there are vulnerabilities in weblogic. Among the information currently published on the Internet, there is no better way to determine whether weblogic has vulnerabilities.
- Safety 1812 2023-05-16 11:16:06
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- How to understand grub password
- The grub password is divided into: whole area password (you need to enter the grub global password to modify the grub label after setting) and menu password (you need to enter the grub menu password to boot the system after setting). If you forget the grub global password, you can enter the rescue mode (rescue, similar to winPE). Reset the grub password. In addition to plain text, the grub password can also use encrypted cipher text. grub encryption tools include: grub-md5-crypt and grub-crypt grub-md5-crypt: MD5 encrypt the password and output grub-crypt: If possible, select the encryption method --md5, --sha-256, --sha-512 ( Default) Edit text
- Safety 1591 2023-05-16 10:13:05
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- What details need to be paid attention to in web testing?
- 1. Page display part (1) First, pay attention to whether the page can be displayed completely, including whether different browsers can display it completely. In actual tests, it is often found that some pages or pop-up windows on the page cannot be fully displayed (2) Whether the animation effect or font effect can be displayed correctly (3) Whether there are default prompts for some form items, input boxes, input fields, and drop-down boxes on the page, and whether some prompts and some do not prompt (4) There are multiple items in the data list Whether the data is displayed in pages, and whether the page jumps normally after the paging operation. 2. Page resolution: Does the page layout display normally in the resolution mode of 640x400, 600x800 or 1024x768? Is the font too small to be browsed? Or is it too large? ?
- Safety 1497 2023-05-16 09:55:05
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- What is the difference between raid0 and raid1 in windows
- The difference between raid0 and raid1 1. Concept 1. RAID0: RAUD0 is the simultaneous writing and reading of multi-disk data groups. 2. RAID1: RAID1 means simultaneous writing and reading of data on multiple disks. 2. Security 1. RAID0: No data backup function and poor security. 2. RAID1: The disks back up each other and have high security. 3. Performance 1. The theoretical read and write speed of RAID0 is X times that of a single disk, where X refers to the number of disks added to the same array. At the same time, the capacity is also X times that of a single disk. 2. The read and write speed of RAID1 is the same as that of a single disk, and the capacity is that of a single disk. Detailed introduction to raid0: RAID0 continuously splits data in units of bits or bytes, reads/writes on multiple disks in parallel, and has high data
- Safety 3040 2023-05-16 09:07:13
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