The OSI model serves as a standard for how applications communicate with one another over a network. An OSI reference serves as a roadmap for suppliers and developers to ensure digital communication hardware and software interoperability.

The OSI layers are as follows:

• Physical layer: Digital data transmission from sender to receiver via a communication medium.

• Data Link Layer: Encodes and decodes data bits and controls data transfer to and from the physical link.

• Network Layer: Forwards packets and offers routing channels for network communication.

• Transport Layer: Ensures end-to-end network connection by dividing the data from the layer above, sending it to the network layer, and verifying the recipient received all the data.

• Session Layer: Establishes and manages a session-layer connection between the sender and the recipient. In addition to starting, halting, and controlling the session, it is responsible for establishing, maintaining, and synchronizing contact between the sender and the receiver.

• Presentation Layer: Displays the data in a suitable manner and structure.

• Application Layer: Interface between the network and the application, emphasizing process communication on a communication interface.

Brute force is a method for accessing credentials by trial and error — continually attempting all possible combinations of credentials until you hit the right one. Here’s how you can avoid brute force attacks:

• Maximum Length Password: Specify the maximum length of a password, so it becomes harder to find the right combination.
• Password Complexity: Requiring many character types in the password makes brute force attacks more difficult. You might establish requirements for special characters, upper- and lower-case letters, and numbers.
• Limiting Login Attempts: Establish a cap on failed login attempts, which makes it impossible to try all possible password combinations.

Secure servers encrypt and decode data using the Secure Sockets Layer (SSL) protocol to prevent unauthorized access to it.

Here are four fast ways to safeguard a server:

• Step 1: Make sure your root and administrator account passwords are safe.

• Step 2: Create new users to manage the system.

• Step 3: Ensure the root and administrator accounts cannot access the internet by default.

• Step 4: Configure your firewall rules for remote access.

Here are the steps to install a firewall:

• Username/password: Change a firewall device’s default password
• Remote administration: Turn off the remote administration feature.
• Port forwarding: Set up the proper port forwarding to ensure applications like a web or FTP server function properly.
• DHCP server: Disable the firewall’s DHCP server to ensure no conflict.
• Logging: Enable logging and learn how to view logs to fix firewall problems or potential assaults.
• Security policies: Establish strong, enforceable security policies for your firewall.

Both HIDS (Host IDS) and NIDS (Network IDS) are intrusion detection systems that find intrusions. Programmers employ the HIDS on a specific host or device — the only distinction. It keeps an eye on a device’s suspicious system activity and traffic. However, NIDS is configured on a network. It keeps track of every network device’s traffic.

A three-way handshake is a procedure used in a TCP/IP network to establish a client-host connection and exchange packets. Here’s the three-step procedure:

• The client sends an SYN (synchronization) to check for available ports and whether the server is online.
• If the client has open ports, the server will send an SYN-ACK message.
• The client acknowledges the message and returns an ACK(Acknowledgment) packet to the server.

Cryptography assures secure communication even with malicious outside actors or adversaries. An algorithm and a key are used in encryption. The key converts plaintext from input into an encrypted output (i.e., cipher text). The same plaintext will always be converted into the same ciphertext if the same key is used, according to a particular algorithm.

Using a table or spreadsheet to hold test data, data-driven testing is a method of software testing. With data-driven testing, testers can create a single test script that can execute tests on all test data from a table and anticipate that the test results will be delivered in the same table. You might also hear data-driven testing referred to as table-driven testing or parameterized testing.

Unit testing

Among the software testing levels, unit testing is the lowest level. The software’s modules or applications are referred to as units. The programmer who tests the modules also performs unit testing, and immediately fixes any discovered bugs.

Integration testing

All of the tested components are combined to form integration, and they are all tested collectively. Data that moves from one module to another is tested as part of integration testing. In essence, it examines the interaction between two or more modules, but not their functionality alone.

System testing

System testing tests the complete or integrated system. It evaluates the software to ensure it complies with standards outlined in the SRS guideline. It conducts both functional and non-functional testing and is the last test.

Acceptance testing

Customers or users conduct acceptance testing to determine whether the product satisfies their needs.

This is one of the most important QA testing interview questions. Sometimes, as a project manager or project lead, we may have to cancel testing to launch the product quicker. In those circumstances, we must determine whether the product has received sufficient testing from testers.

We’d consider:

• If the testing or release deadlines are met.
• If the risk in the real-time project is below the permitted level.
• If all the critical bugs and roadblocks have been resolved.
• If our submission meets the requirements.