DMZ networks are frequently used to: isolate and keep prospective target systems apart from internal networks; lessen and regulate external users' access to such systems;
Why are DMZ zones used in networks?
The goal of a DMZ to safeguard the hosts that are most susceptible to attacks, there is a DMZ network. These hosts typically host services that are accessible to users outside of the LAN, with email, web servers, and DNS servers serving as the most prevalent examples.
What are the techniques for isolating a network?
Techniques for network isolation prohibit network hosts from accessing system network resources that are not absolutely necessary. The number of computers that a host can connect with across their LAN is constrained by broadcast isolation. blocking the domain name value of the response from a reverse DNS search. preventing a reverse search based on IP address of the query.
To know more about DMZ visit:
https://brainly.com/question/27360592
#SPJ4
what are the elements of design security
Firewalls, network monitoring, intrusion detection, vulnerability scanning, risk analysis, and security policies and procedures. Access control. Data encryption are the elements of design security
1. Access Control: Limiting access to only those who have been given permission.
2. Data encryption: The encoding of data to shield it from unauthorized access.
3. Firewalls: Firewalls serve as a partition between internal networks and public networks like the internet.
4. Network monitoring: keeping an eye out for unwanted access or any unusual activity on the network.
5. Intrusion detection systems: Monitoring for any possible malicious activity or unauthorized access attempts.
6. Vulnerability Scanning: Consistently looking for weak spots on the network that attackers might exploit.
7. Risk assessment: determining the system's possible dangers and taking steps to reduce them.
Establishing security rules and processes to guarantee the system's security is step eight.
Learn more about element here:
brainly.com/question/29659345
#SPJ4
What is a good, free to use, and non coding program or app that you can use to develop a video game on a Chromebook? I want to make a game that is like an rpg, but is just like a game of choice, and has a story-line to it.
I want to make my own, but it's hard to find anything that is good, and free with no coding.
If you have ever played Cooking Companions, or Doki Doki Literature Club, I want it to be something like that kind of nature.
A good, free, and non-coding program or app for developing a video game on a Chromebook is Construct 3.
What is the coding program about?It is a browser-based game engine that allows you to create 2D games without any coding required. You can use drag-and-drop tools to create your game and add animations, sound effects, and other features. The platform has a large community and a wide range of tutorials and resources available, making it a great choice for beginners looking to develop their own video games.
Therefore, Construct 3 is a cloud-based game development platform that offers a wide range of features for creating 2D games. The platform provides a visual interface with drag-and-drop tools for game development, so no prior coding experience is required.
Learn more about coding program from
https://brainly.com/question/23275071
#SPJ1
what does rm -r do differently than rm?
So the solution is straightforward. While the rmdir command only deletes empty directories, the rm command can also be used to remove non-empty directories.
Using the rmdir command, non-empty directories cannot be deleted at all. A directory and all of its contents are recursively deleted using the command rm -r (normally rm will not delete directories, while rmdir will only delete empty directories). The git rm command deletes the file from the local file system as well as the git repository. However, the rm command just purges the file from the file system. Simply list all of the file names following the "rm" command to delete many files at once. A space should be used to separate file names. Using the "rm" command.
Learn more about system here-
https://brainly.com/question/30146762
#SPJ4
whether computer can order a week's worth of groceries on the internet?
Computers can handle this problem of ordering groceries for a week's worth of meals online.
Telling your computer what you want, what size (if any), how many, etc., is all that is required. In order for your computer to perform the transaction on your behalf, it would also want access to your payment information. Yes. Such jobs can be performed by software robots, especially if the architecture of the online grocery store does not change significantly over time. Artificial intelligence will be used in grocery stores to help employees and store owners with the strain of physical labor. Grocers can benefit from artificial intelligence in a variety of ways because there are so many different algorithms available: forecast upcoming customer purchases. Make models so that you can sell them.
Learn more about software here-
https://brainly.com/question/18950462
#SPJ4
what is the bit rate for a signal in which 1 bit lasts 5ms
The bit rate for a transmission with a 5ms per bit duration is 0.2kbps. The amount of data or information communicated from a source over a predetermined period of time is referred to as bit rate.
The speed at which data or signals are sent from their source to their destination is referred to as bit rate. In most cases, bit rates are specified in terms of bytes per second or bits per second.
given 1 bit in 5 ms, bit rate Rb=1/5 ms = 1000 / 5 = 200 bits per second = 0.2 kbps
The amount of data or information communicated from a source over a predetermined period of time is referred to as bit rate.
The maximum pace at which bits may be sent from a source to a destination through a specific path or media is known as the bandwidth.
In comparison to traditional communication systems, advanced communication technologies like 4G and 5G support numerous channels and increased data transport.
Learn more about Data here:
https://brainly.com/question/5430107
#SPJ4
vm1 does not have a public ip address. you need to be able to deploy azure bastion to protect vm1. what should you do first?
Log in to the Azure website, access your virtual network Choose Bastion from the left pane on the page for your virtual network to bring up the Bastion page.
Choose Configure manually from the Bastion page. By doing so, you may define certain extra options for Bastion when it is deployed to your VNet.
Set the parameters for your bastion host on the Create a Bastion page. Your virtual network settings are used to populate the project information. Set the values for the instance details.
Set the virtual networks' parameters. From the menu, choose your VNet. Make sure you choose the right Region in the previous settings on this page if you don't see your VNet in the dropdown list.
Select Manage subnet configuration to set the Azure BastionSubnet's setup.
To access the Add subnet page, choose +Subnet on the Subnets page.
Use the following settings to establish the "AzureBastionSubnet" subnet on the Add subnet page. Leave the other settings alone.
Learn more about Azure here:
https://brainly.com/question/13144160
#SPJ4
You have an Azure virtual network named VNET1 that has an IP address space of 192.168.0.0/16 and the following subnets:
Subnet1- has an IP address range of 192.168.1.0/24 and is connected to 15 VMs
Subnet2- has an IP address range of 192.168.2.0/24 and does not have any VMs connected
You need to ensure that you can deploy Azure Firewall to VNET1.
What should you do?
A. Add a new subnet to VNET1.
B. Add a service endpoint to Subnet2.
C. Modify the subnet mask of Subnet2.
D. Modify the IP address space of VNET1
We should Add a new subnet to VNET1 to ensure that we can deploy Azure Firewall to VNET1.
What is Azure Firewall?
Azure Firewall is a cloud-based network security service that provides centralized network traffic control for Azure virtual networks. It acts as a stateful firewall-as-a-service, allowing administrators to define and enforce network security policies across virtual networks. Azure Firewall uses the same configuration and policy definitions as traditional firewalls, and it is fully integrated with Azure services and applications
A. Add a new subnet to VNET1.
Adding a new subnet to VNET1 would allow for the deployment of Azure Firewall. The new subnet would act as a dedicated network for the firewall to reside in and manage network traffic. This new subnet should have a sufficient IP address range to accommodate the firewall and any additional resources that may be added in the future.
Learn more about Azure Firewall click here:
https://brainly.com/question/14533851
#SPJ1
as a i will create the user stories before sprint planning so that the team knows what the specific requirements are in the form of a story by a user.
The product owner Compiler and organizes the product backlog prior to sprint planning so that the team is aware of the work that is scheduled and the importance of the user stories.
The product owner is the one who is in charge of developing the product backlog on behalf of the stakeholders, however, he can enlist the assistance of the scrum master and the development team.
Before sprint planning, the product owner writes user stories to let the team know what the precise requirements are in the form of a user's story. During the sprint, the team members select the story's requirements and functionality after the product owner presents it for approval.
Compiler: A piece of software that converts source code written in a high-level language (such as C++) into a set of instructions that can be read by the CPU of a digital computer. Large-scale programs called compilers have error-checking and other features. Some compilers convert high-level languages into intermediate assembly languages, which are then converted (assembled) into machine code by an assembly program or assembler. Other compilers produce machine language straight away. Grace Hopper, an American computer scientist who created one of the first compilers in the early 1950s, is credited with coining the term "compiler."
Learn more about Compiler here:
https://brainly.com/question/4896128
#SPJ4
which types of positions is job analysis modeling most applicable
Job analysis modeling is most applicable for some specific type of positions.
Job analysis refers to a systematic process of collecting all information about a specific job, including skill requirements, roles, responsibilities and processes in order to create a valid job description.
Job analysis is most applicable for positions like training, recruiting and selection, performance management .It basically is more concern about the personal attributes.
Steps in position of job analysis modeling
STEP 1: COLLECT INFORMATION ABOUT THE JOB.
STEP 2: LIST THE TASKS.
STEP 3: IDENTIFY THE CRITICAL TASKS.
STEP 4: IDENTIFY THE CRITICAL COMPETENCIES.
Learn more about job analysis here:-
brainly.com/question/29802928
#SPJ4
what is an example of applying cadence-based synchronization in safe?
Safe's cadence-based synchronization can be used to ensure that data is backed up on a regular basis. Depending on the needs of the user, a system may be configured to back up data every hour, day, week, or month.
Safe uses cadence-based synchronization to make sure that data is routinely backed up and securely stored. Setting a certain backup frequency, such as hourly, daily, weekly, or monthly, will enable you to accomplish this. This gives the user the ability to track the backup of their data and can be used to make sure that all data is current and secure. Additionally, it enables the user to specify parameters for the backup procedure, such as the kind of files that are backed up, where the files are stored, and more. Data loss and corruption may be prevented, and cadence-based synchronization can give users the assurance that their data is routinely backed up and kept securely.
Learn more about synchronization here-
https://brainly.com/question/15293990
#SPJ4
true/false: you can nest a for loop inside another for loop, but cannot nest a while loop inside another while loop or a do-while loop inside another do-while loop.
Answer:
False. You can nest a while loop inside another while loop, and a do-while loop inside another do-while loop, just as you can nest a for loop inside another for loop.
why do different ip networks need to be assigned to different ports of a router?
For effective traffic segmentation and routing, various IP networks must be assigned to different ports of a router. This aids in ensuring proper data routing and avoiding network sluggishness.
For effective traffic segmentation and routing, various IP networks must be assigned to different ports of a router. This aids in ensuring proper data routing and avoiding network sluggishness. When multiple networks are linked to a single router, the router can transport data from one network to another without having to process traffic from both networks at once by allocating each network to a different port. Additionally, by separating traffic from several networks, this helps to avoid network congestion. As each network can be given its own security settings, allowing for tighter control over who can access the network, having several networks on different ports also aids in enhancing security. Additionally, using various networks on various ports.
Learn more about network here:
brainly.com/question/29970297
#SPJ4
how to do codehs camp lesson 2.10
The correct answer is CodeHS Certifications provide as proof that students have acquired knowledge and abilities via our thorough, secure test.
Certifications will also assist in promoting the computer science programme at your institution by giving students and potential employers more confidence in your program's abilities. CodeHS is a dynamic online learning environment that provides both classroom and individual education in computer science and programming. Through the provision of online learning resources and the assistance of remote instructors, CodeHS aims to increase access to and knowledge of computer science. We at CodeHS are pleased to offer our extensive online courseware without charge! Create an account, set up lessons, sign up your students, and get them started on their own CS route to get started right now.
To learn more about CodeHS click the link below:
brainly.com/question/26099830
#SPJ4
using email or fake websites to induce you to provide personal information through a website is called cyberstalking. true false
Answer:
true
Explanation:
because when you do that they can trace were your location or device is
A Hopfield network has 20 units. How many adjustable parameters does this network contain?A. 95B. 190C. 200D. 380E. 400
A Hop field network has 20 units. There will be 190 adjustable parameters this network contains. The correct option is B.
What is a Hopfield network?A Hopfield network is a single-layered, recurrent network in which each neuron is connected to every other neuron, making it completely interconnected.
The Hopfield network model's network capacity is based on the number of neurons and their connections inside a specific network. As a result, neurons and connections play a role in how many memories can be stored.
Therefore, the correct option is B. 190.
To learn more about Hopfield network, refer to the link:
https://brainly.com/question/29993625
#SPJ1
synchronized security automates detection, isolation and remediation results for endpoints?
Sophos solutions actively collaborate with one another through Synchronized Security, automatically responding to incidents and providing improved security insights.
Sophos solutions communicate real-time data using a proprietary Security HeartbeatTM and react instantly, within seconds. The first and finest cybersecurity system in the world is called Synchronized Security. Products for endpoints, networks, mobile devices, Wi-Fi, email, and encryption, all of which share information instantly and react to incidents automatically: Block lateral movement by isolating contaminated endpoints. The MAC addresses of all a device's network interfaces are shared by the firewall with other endpoints when it detects a red Security Heartbeat condition, and those endpoints use the Windows Firewall to block all traffic from those MAC addresses.
Learn more about security here-
https://brainly.com/question/29793041
#SPJ4
which topics should be discussed in the sprint review?
The topics that should be discussed in the sprint review are the Scrum process, coding and engineering practices, and sprint results. The correct option is d. all the above.
What is sprint review?The team presents what was completed during a sprint review, an informal meeting held at the conclusion of a sprint during which the stakeholders offer input. It is a collaborative working session as opposed to a monologue.
The following components make up the Sprint Review: The Product Owner has invited the Scrum Team and other important stakeholders to attend.
Therefore, the correct option is d. All the statements.
To learn more about sprint review, refer to the link:
https://brainly.com/question/29543960
#SPJ1
The question is incomplete. Your most probably complete question is given below:
a. The Scrum process, and how it was used during the Sprint.
b. Coding and engineering practices.
c. Sprint results.
d. All of the statement
after a host has generated an ipv6 address by using the dhcpv6 or slaac process, how does the host verify that the address is unique and therefore usable?
Note that after generating an IPv6 address, the host uses the Neighbor Discovery Protocol (NDP) to verify the uniqueness of the address. The host sends a Neighbor Solicitation (NS) message to the network, which checks for duplicate addresses. If no duplicate is found, the network sends a Neighbor Advertisement (NA) message, confirming that the address is unique and can be used by the host. This process is known as Duplicate Address Detection (DAD).
What is ipv6?The most current version of the Internet Protocol, the communications protocol that provides an identifying and location system for computers on networks and directs data across the Internet, is Internet Protocol version 6.
An IPv6 address is 128 bits long and is made up of eight 16-bit elements, each separated by a colon. In contrast to the dotted-decimal syntax of IPv4 addresses, each field must include a hexadecimal value. The x's in the following diagram indicate hexadecimal numbers.
Learn more about ipv6:
https://brainly.com/question/15733937
#SPJ1
malware that changes its binary pattern on specific dates at specific times to avoid detection is known as a (n):
Malware that changes its binary pattern on specific dates at specific times to avoid detection is known as a polymorphic virus. The correct option is C.
What is a polymorphic virus?A polymorphic virus, also known as a metamorphic virus, is a type of malware that is designed to repeatedly alter its signature files or outward appearance by utilizing new decryption techniques.
A polymorphic virus is a sort of malicious software that may alter or "morph," making it challenging to find using antimalware solutions.
Therefore, the correct option is C. polymorphic virus.
To learn more about malware, visit here:
https://brainly.com/question/15013689
#SPJ1
The question is incomplete. Your most probably complete question is given below:
A. armored virus
B. logic bomb
C. polymorphic virus
D. Trojan
To get started in terms of what to build, Scrum requires no more than a Product Owner with enough ideas for a first Sprint, a Development Team to implement those ideas and a Scrum Master to help guide the process. True or False?
True. Scrum does not require any complex tools or processes to begin, only the definition of what is necessary data to develop the product. The Product Owner provides the ideas, the Development Team builds the product, and the Scrum Master facilitates the process.
True, Scrum does not require any complex tools or processes to begin. All that is needed is for the Product Owner to provide enough ideas for the first Sprint, a Development Team to implement those ideas, and a Scrum Master to facilitate the process. The Product Owner is the person responsible for managing the product's success. They provide the overall vision and direction, create a prioritized list of features, and provide feedback on the progress of the product. The Development Team is responsible for the actual implementation of the product. They write the code, create the designs, and test the product. Finally, the Scrum Master is responsible for guiding the process, helping to ensure that the product is delivered on time and within budget. They are also responsible for ensuring that the team is staying on track and following the Scrum framework.
Learn more about data here-
brainly.com/question/11941925
#SPJ4
ben wants to review the sales of a particular product laptop. which element of the lens is used to add the constraint?
The filter allows Ben to narrow down the results to the specific product he is interested in reviewing, so he can focus on the sales of that particular laptop. By adding the filter, Ben can quickly and easily review the sales of the laptop by isolating the relevant data and reviewing it in a more efficient manner.
The element of the lens used to add the constraint in this scenario is the filter. This element of the lens allows Ben to narrow down the results to the specific product he is interested in reviewing. By adding the filter, Ben can quickly and easily review the sales of the laptop without needing to sift through larger datasets. The filter allows Ben to focus on the sales of the laptop he is interested in, by isolating the relevant data. This makes it easier and more efficient for Ben to review the sales of the laptop and allows him to concentrate on the data that is relevant to his query. Without the use of the filter, Ben would have to manually search through the data, which may take more time and energy. The use of the filter allows Ben to review the sales of the laptop quickly and efficiently.
Learn more about laptop here:
brainly.com/question/15244123
#SPJ4
1. write a pl/sql program using cursor which displays all employees’ names, employees’ salaries, their managers’ name and managers’ salaries from emp table.
This PL/SQL programme utilises a cursor to display all employees' names, salaries, and the names and salaries of their corresponding managers from the "emp" table.
This PL/SQL software iterates through the "emp" table to display all employee names, salaries, and the names and salaries of their corresponding managers. An SQL statement called a CURSOR creates a context area for processing a query's results when it is executed. An active set is another name for this contextual area. Each row of the "emp" table will be individually fetched by the cursor, which will then store the data in the context area before displaying it. The programme will begin by announcing a CURSOR that will choose the names, salaries, and titles of each employee as well as the names and titles of each management. The data is then retrieved and stored in the context area when this SELECT statement is OPENED.
Learn more about SQL here:
brainly.com/question/20264930
#SPJ4
what is the primary reason why emergency services communications (phone or radio) are recorded?
The answer states that, if necessary, communications may be included in a legal record.
What does the term "communications" mean?Transmit and receive messages through both verbal and non-verbal means is the process of communication. The goal of communication is to create understanding amongst two or more people by sharing data in the shape of thoughts, views, and ideas in a two-way fashion.
What do jobs in communications do?These experts create and preserve a company's engagement with the general public. They develop social media strategy, manage information production, maintain public relationships, and create news releases. At reduced ranks, they could narrow their attention to only one facet of a company's communication plan.
To know more about Communications visit :
https://brainly.com/question/15059972
#SPJ4
what is the negative impact of misconfiguration & third-party of vpns policies ?
Incorrect configuration and unauthorised access brought on by third-party VPNs can result in virus and malware attacks as well as data loss.
Network security may suffer from improper configuration and outside VPNs. Third-party VPNs can be challenging to secure and might not adhere to the same level of security as in-house VPNs, while poorly setup VPNs might be exposed to unauthorised access, allowing hostile actors to access sensitive data. Furthermore, third-party VPNs might be infected with spyware or ransomware, further eroding network security. Misconfigured and third-party VPNs can open an unsecured gateway for nefarious actors to access sensitive data without adequate configuration, monitoring, and maintenance. As a result, it's crucial to make sure that all VPNs are correctly installed and kept an eye out for any unusual activity.
Know more about malware:
brainly.com/question/14276107
#SPJ4
For the purpose of this discussion, consider a scenario where you manage more than 100 Windows 10 devices and are asked to provide input on allowing users to customize items such as the Start Menu.
What settings should you allow users to change, and what settings should be controlled by the system administrator?
What are the advantages and disadvantages?
How does the industry of the organic? I zation play a role in your answer?
The Start Menu's size and organization, as well as the ability to pin and unpin programs, are settings that should be open to user customization. Deeper system settings including user access, security precautions, and system updates should be within the administrative authority of the system.
Administrators should think about which features users should be able to change before allowing them to personalize the Start Menu. Users ought to be able to pin and unpin programs from the Start Menu, as well as change the size and arrangement of the Start Menu's contents. Users can alter these options to fit their preferences and requirements and personalize their Start Menu. Deeper system settings including user access, security precautions, and system updates should be within the administrative authority of the system. By preventing unauthorized users from accessing particular parts of the system, the security of the system is maintained.
Learn more about program here-
brainly.com/question/11023419
#SPJ4
sketch the time relative appearance of voltage waveforms produced by this wind vane sensor for direction explain what information the micro computer must have available
The waveform for direction produced by the wind vane sensor is displayed below. In order for the microcomputer to understand the waveform, it needs knowledge of the wind speed, direction, and measurement time.
The wind direction is depicted in the waveform produced by the wind vane sensor for direction. The waveform's beginning symbolizes the direction of the wind at the time it is being measured, and each peak and trough of the waveform denotes a shift in the direction of the wind. Each cycle of this waveform's cyclic pattern, which repeats itself over time, corresponds to a shift in the measurement's wind direction. In order for the microcomputer to understand the waveform, it needs knowledge of the wind speed, direction, and measurement time. The microcomputer can use this data to identify the moments when the wind changes direction and to pinpoint the direction of the wind at each point.
Learn more about microcomputer here:
https://brainly.com/question/27948744
#SPJ4
Which 2 batch actions can be performed in the customer center in QuickBooks online?
A. Delete
B. Assign a customer type
C. Make inactive
D. Change currency
E. Assign project
The 2 batch actions can be performed in the customer center in QuickBooks online are:
A. Delete
C. Make inactive
What is the QuickBooks about?In QuickBooks Online's customer center, two batch actions that can be performed are:
A. Delete: This allows the user to delete multiple customers at once instead of having to do so one by one. This can save time when needing to clean up the customer list.
C. Make Inactive: This allows the user to mark multiple customers as inactive, which means they will not show up in certain reports or drop-down lists within QuickBooks. This can be useful when a customer is no longer active or no longer using the business's services.
Note: The availability of these actions may depend on the user's QuickBooks Online plan and their permissions.
Learn more about QuickBooks from
https://brainly.com/question/24441347
#SPJ1
jared is a system administrator for an international trading company. all employee computers are required to run windows 10 professional and are currently running version 1703. the company it department uses azure active directory and microsoft intune (as the mdm) to enroll and manage the computer devices. using the microsoft 365 device management administrative portal, jared has created a group for the sales representatives' computers, created an autopilot deployment profile, and configured the out-of-box experience (oobe) settings so that:
Email the employee a file called a provisioning package (.ppkg) for them to install on the laptop.
Is Jared employed by an import distribution company as a systems engineer?Jared works as a system engineer for an import distribution company with offices in the United States, Asia, and Europe. He currently protects all of the company's devices with Microsooft Defender Advanced Threat Protection (Microsoft Defender ATP).
If Windows 10 is not already activated, which of the following would require you to enter a product key to activate it?A product key is required for activation when: Windows 10 can be purchased either as a physical product or as a digital download from a retailer or authorized reseller. -There is no digital license for you. -Your company has a volume licensing agreement with Microsoft for Windows 10.
To know more about provisioning package visit :-
https://brainly.com/question/30030670
#SPJ4
multiple select question select all that apply what are some traits of a good subject line in an email to an instructor? multiple select question.
Some traits of a good subject line in an email to an instructor are:
Be specific, clear, and concise.Follow any rules the instructor has for what should be in a subject line. Identify the focus of the email.Definition of e-mailEmail is an abbreviation of Electronic Mail or in Indonesian it is called Electronic Letters which is a means of sending letters through internet media. The internet media in question can be via a computer or cellphone that has internet access. In general, sending regular mail will incur a fee (buying postage) but electronic mail only requires an internet connection.
E-mail FunctionEmail is our official address in cyberspace. By using e-mail we can connect to various internet activities, such as joining social networking sites.
Learn more about email at https://brainly.com/question/14666241.
#SPJ4
What are two significant risks that can be understood from the program board? (Choose two.)
1.) A Feature has an excess of dependencies and risks associated with it
2.) Team work in process (WIP) limits are being ignored
3.) Teams do not understand their Features and Epics
4.) No work is planned for the Innovation and Planning (IP) Iteration
5.) Features are being delivered at the end of the last Iteration
The two significant risks that can be understood from the program board are Features with too many dependencies may fail or experience delays. 2. Ignoring WIP limitations might result in resource overload and missed deadlines.
1.) Too many dependencies in a feature can cause the program's delivery to be delayed or to fail altogether. This is so because dependencies may result in problems such a lack of tools, information, or communication. When features have too many dependencies, it might be challenging to keep the timetable on track because each dependence must be managed, recorded, and taken care of individually.
2. Ignoring WIP limitations might result in resource overload and missed deadlines. This is because a team is less likely to give each task the attention it requires if they are working on too many activities at once. This may cause things to take longer than they should or to be finished with lesser quality than planned. Teams are also more likely to miss deadlines when WIP limitations are disregarded because of the volume of work that needs to be done.
Learn more about program here-
brainly.com/question/11023419
#SPJ4