Penetration testers favor Nmap due to its ease of use, powerful scanning option, and clean installation. Likewise, several systems and network administrators find Nmap valuable for day-to-day activities, including monitoring service or host uptime, network inventory, and handling service upgrade schedules. This, among other reasons, has added to its popularity and widespread use.
One way for you to learn more about Nmap and gain hands-on experience is to sign up for the . This will also help you increase your job prospects in penetration testing, up your skills, and find ways to climb the corporate ladder.
What is the purpose of Nmap?
Nmap, also called Network Mapped, or Network Mapper, is a popular host detection, service, and operating system detection, as well as a network scanning device that helps with penetration testing. It is one of the most common free and open-source network discovery tools on the market today.
Nmap is mostly used by Ethical Hackers to discover services and hosts on a computer network by sending packets and evaluating their responses. This program has become known as a fundamental program for network administrators who want to map out their networks and perform broad network inventories.
Nmap initially emerged as a Linux utility and was ported to other systems such as BSD, Windows, and macOS, and BSD. Nmap is even more popular on Linux than Windows. Some of the common uses of Nmap include:
- Auditing network security through detecting new servers.
- Auditing the security of a firewall or gadget by pinpointing the network connections that can be made through it.
- Discovering and exploiting software vulnerabilities.
- Recognizing open ports on a target host while planning for auditing.
- Performing network mapping, network inventory, and asset management.
- Creating traffic to hosts on a network, applying response time measurement, and conducting response analysis.
- Executing DNS queries and subdomain searches.
Is using Nmap illegal?
Using Nmap is not exactly an illegal act since no federal law in the United States explicitly bans port scanning. Effective use of Nmap can protect your system network from intruders. However, unapproved port scanning for whatever reason can get you jailed, fired, disqualified, or even prohibited by your ISP.
The legal implications of scanning networks with Nmap utilities are complicated and extremely controversial, such that it draws several heated but unproductive discussions. The best way to avoid controversy and risks when using Nmap is to:
- Read in-depth legal guides about Nmap
- Speak to a knowledgeable lawyer within your jurisdiction to gain an understanding of the laws about your situation, and
- Constantly obtain written authorization from the target network agents before beginning any scanning whatsoever.
How does Nmap work?
Nmap is a powerful software that requires detailed background knowledge of how it works before it can be used properly. Nmap works by inspecting a network for services and hosts. The moment the hosts and services are found, Nmap transfers information to them, to which they respond. This software platform reads and deciphers the response received and applies the information to generate a map of the network.
The generated map consists of detailed information about what each port is doing, who or what is using it, how the hosts are being connected, what is or isn’t making it through the firewall, and a list of all the security issues (if any) that surfaces.
Nmap accomplishes all these through a multifaceted system of scripts that interacts with every aspect of the network. This scriptable interaction functions as communication devices between human users and the network components.
These scripts can be used to perform many functions including, network discovery, backdoor detection, vulnerability detection, and vulnerability exploitation. You can take a penetration testing course online to learn more about how to use Nmap. For more information, click here!
What are the three main functions of Nmap?
Nmap offers several features for each of a penetration testing task including
- Port Scanning: Nmap can be used for enumerating the open ports on target hosts
- Host Discovery: Nmap is beneficial for identifying hosts on a network such as itemizing the hosts that have certain open ports or those that respond to ICMP or TCP requests
- Version Detection: another function of Nmap is its ability to interrogate network services on remote devices to verify version numbers and determine application names.
Other functions of Nmap include
- OS Detection: Nmap tools help to determine the operating system and hardware features of network devices.
- Scriptable interaction with the target: Nmap offers additional information about a target, such as their device types, DNS names, or MAC addresses. Scripting interactions with targets are conducted through the Scripting Engine (NSE) and Lua programming language.
Why do cybercriminals use Nmap?
Most cybercriminals use Nmap for Nmap to obtain access to unrestrained ports on a system. The cybercriminal merely needs to effectively get into a specific system to run Nmap on that system, be on the lookout for software vulnerabilities, and make plans to exploit those vulnerabilities.
Malicious hackers aren’t the only experts who exploit Nmap. IT security companies employ the services of penetration testers who use this software platform to replicate the possible attacks that a network or system could face in the long run. This helps the security administrator understand the existing weaknesses that a hacker can exploit.
Learn more about Nmap tools by signing up for the EC-Council Certified Security Analyst (ECSA) training program and learn how to use Nmap for Penetration Testing.
Types of Nmap Scan
There is a long list of scan types that can be executed using Nmap. However, the following are three popular types.
This scan type is commonly applied to inspect and finish a three-way handshake between the user and the target system. Unlike other types of scans, a TCP scan is usually slow and systematic. A TCP scan can easily be detected because it is usually noisy.
UDP scans are applied to confirm if there is any UDP port that is open or vulnerable. UDP is a connectionless protocol, unlike TCP, and it lacks the structure to respond with a positive acknowledgment. As such, there is constantly a possibility for a false positive in the scan outcomes.
This is a variant of the TCP scan. However, the difference between a TCP scan and the SYN scan is that in a syn scan, the Nmap itself crafts a syn packet, which is initially sent to generate a TCP connection. In an SYN scan, the connection is never created. Instead, Nmap analyses the responses to those personally created packets to generate scan results.
Other scan types include:
- ACK Scan
- FIN Scan
- XMAS scan
- NULL Scan
- IDLE Scan
- RPC Scan
What is the default Nmap scan?
By default, Nmap will perform an SYN scan when scanning TCP ports unless if the user does not have sufficient privileges. In that case, it will fall back to a connect scan. When an SYN scan is not an option, TCP connects scan is usually the default option.
SYN scan is the default and most common scan selection for several reasons. SYN scan can be executed speedily, and it can scan thousands of ports per second when connected to a fast network without being hindered by constricting firewalls.
How long does the Nmap scan take?
The amount of time it takes to conduct Nmap scans is determined by several factors, including the number of hosts you plan to scan. Some firewall configurations, predominantly, response rate limiting can affect scan times. Besides, some scan selections, including UDP scanning and version detection, can also upsurge scan times considerably.
The program upholds a running timeout value for shaping the duration of time it will take for a probe response before retransmitting the probe or giving up. This is analyzed depending on the response times of former probes. Supposing the network latency displays itself to be variable and substantial, the timeout can increase to more than a few seconds.
Ultimately, the user has control over how Nmap runs, even with its parallelism and several advanced algorithms used for scanning. You can reduce scan times by excluding non-critical tests, optimizing timing parameters, or upgrading to the latest version of Nmap. All these can make a considerable difference to scan times and enhance performance.
About EC-Council Certified Security Analyst (ECSA)
EC-Council Certified Security Analyst (ECSA) is a penetration testing online certification program that provides you with a hands-on penetration testing experience. Unlike most other penetration-testing programs that fundamentally trail a standard “kill chain methodology,” the ECSA program presents a set of uniquely broad methodologies that are capable of covering diverse pen testing requirements across different verticals.
Likewise, the ECSA (Practical) is a 12-hour long practical exam meant to test your penetration testing skills. It also tests competence in writing your exploits, executing threat and exploit research, recognizing exploits in the wild, and making critical decisions at the diverse stages of a pen testing engagement, which can either make or mar the whole assessment. For more information about ECSA and ECSA (Practical), click here!