Security Interview Questions

Security Interview Questions

1) What is data encapsulation?

Data Encapsulation is a process of hiding and protecting data from the outside users or interference. The sending and receiving of data from a source device to the destination device is possible with the help of networking protocols when data encapsulation is used. Protocol Data Units contain the control information attached to the data at each layer. The information is attached to the data field’s header but can also be at the end of the data field or trailer. PDUs are encapsulated by attaching them to the data at each OSI reference model layer.

2) What is VPN?

A virtual private network (VPN) is a technology that offers secure, reliable connectivity over a shared public network infrastructure such as the Internet. VPNs maintain the same security and management policies as a private network. They are the most cost effective method of establishing a virtual point-to-point connection between remote users and an enterprise customer's network.

3) Briefly describe NAT.

Network Address Translation (NAT) is designed for IP address conservation. It enables private IP networks that use unregistered IP addresses to connect to the Internet. NAT operates on a router, usually connecting two networks together, and translates the private (not globally unique) addresses in the internal network into legal addresses, before packets are forwarded to another network. Also, NAT can be configured to advertise only one address for the entire network to the outside world. This provides additional security by effectively hiding the entire internal network behind that address. NAT offers the dual functions of security and address conservation and is typically implemented in remote-access environments.

4) What is the job of the Network Layer under the OSI reference model?
Network layer is third layer in the OSI Model, it handle routing and prepare data for transmission. Primary functions are communication with the Transport/ data link layer ; Encapsulation of Transport data into Network layer Protocol Data Unit; Management of connectivity and routing between hosts or networks.
5) What are proxy servers and how do they protect computer networks?

Proxy server is a server may be a computer system or an application that acts as an intermediary for requests from clients seeking resources from other servers and client connects to the proxy server, requesting some service, such as a file, connection, web page or other resource available from a different server and the proxy server evaluates the request as a way to simplify and control its complexity. A proxy can keep the internal network structure of a company secret by using network address translation, which can help the security of the internal network and this makes requests from machines and users on the local network anonymous

6) What is the function of the OSI Session Layer?

In OSI model, the session layer is the fifth layer, which controls the connections between multiple computers. The session layer tracks the dialogs between computers, which are also called sessions. This layer establishes, controls and ends the sessions between local and remote applications. session layer software products are more sets of tools than specific protocols. These session-layer tools are normally provided to higher layer protocols through command sets often called application program interfaces or APIs. Common APIs include NetBIOS, TCP/IP Sockets and Remote Procedure Calls (RPCs). They allow an application to accomplish certain high-level communications over the network easily, by using a standardized set of services. Most of these session-layer tools are of primary interest to the developers of application software. The programmers use the APIs to write software that is able to communicate using TCP/IP without having to know the implementation details of how TCP/IP works.

7) What is DoS?

The Denial of Service (DoS) attack is focused on making a resource (site, application, server) unavailable for the purpose it was designed. There are many ways to make a service unavailable for legitimate users by manipulating network packets, programming, logical, or resources handling vulnerabilities, among others. If a service receives a very large number of requests, it may cease to be available to legitimate users. In the same way, a service may stop if a programming vulnerability is exploited, or the way the service handles resources it uses. Sometimes the attacker can inject and execute arbitrary code while performing a DoS attack in order to access critical information or execute commands on the server. Denial-of-service attacks significantly degrade the service quality experienced by legitimate users. These attacks introduce large response delays, excessive losses, and service interruptions, resulting in direct impact on availability.

8) What is OSI and what role does it play in computer networks?

The OSI (Open Systems Interconnection) serves as a reference model for data communication. It is made up of 7 layers, with each layer defining a particular aspect on how network devices connect and communicate with one another. Upper layers of the OSI model represent software that implements network services like encryption and connection management. Lower layers of the OSI model implement more hardware-oriented functions like routing, addressing, and flow control.

9) What is the main purpose of OSPF?

The OSPF (Open Shortest Path First) protocol The OSPF protocol is a link-state routing protocol which means that the routers exchange topology information with their nearest neighbours. The topology information is flooded throughout the Autonomous System, so that every router within the Autonomous System has a complete picture of the topology of the Autonomous System. This is then used to calculate end-to-end paths through the Autonomous System, normally using a variant of the Dijkstra algorithm. Therefore, in a link-state routing protocol, the next hop address to which data is forwarded is determined by choosing the best end-to-end path to the eventual destination.

10) What is the main job of the ARP?

Address Resolution Protocol (ARP) feature to translate physical addresses to internet protocol (IP) addresses. A physical address can be the MAC (Media Access Control) address of a network card inside of a computer. The information about which hardware address is associated with which IP address is usually stored in a table on each computer, the so-called ARP table.

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