Penetration testing helps security researchers uncover vulnerabilities that a hacker may potentially exploit to compromise an entire tech stack, network, or web application. An enumeration pentest is one such penetration technique that helps determine whether device configurations have been appropriately implemented, apart from helping to meet compliance requirements and develop guidelines for security training and awareness.
This article discusses the importance of enumeration in cybersecurity while learning various enumeration pentest techniques and use cases.
What is Enumeration in Cybersecurity?
Often termed the second phase of penetration testing, an enumeration technique is used to gather the information that helps cybersecurity teams to identify system weaknesses and map out the network’s attack surface.
Before the exploitation phase, penetration testing often involves reconnaissance and enumeration to discover potential attack vectors within network resources. During the second enumeration phase, penetration testers establish an active connection to a remote machine in the network to gather information such as valid usernames, routing tables, TCP ports, machine names, etc.
Enumeration is considered a crucial part of the penetration testing process as it provides an insight into metrics and outcomes that are directly used to craft exploits and test the system’s security flaws.
Some techniques used to discover security flaws include:
1. Using default passwords to test the robustness of the authentication protocol
2. Comprehensive authentication validation to prevent exploits of the authentication process
3. Using email IDs to determine valid and invalid username entries
4. Using Windows Active Directory to extract client workgroup information
5. Leveraging IP tables and DNS entries to access information on domain structure, tool web links, device type, anonymous connections, and file shares across the network
Enumeration also helps penetration testers obtain detailed end-to-end information on what is to be tested in target hosts, allowing for a holistic assessment of the attack surface.
Significance of Enumeration in Penetration Testing
Enumeration is considered one of the most powerful techniques in ethical hacking to identify comprehensive vulnerabilities of a system. Some common use cases of enumeration in pentesting include:
Compliance and regulation
For security audit and compliance purposes, it is crucial to catalog the entire system and network resources, including primary servers, domain user registries, current user information, the list of tools used to deploy services, and service settings. Enumeration helps identify all machines and services within the network while categorizing them based on identified attack vectors and security posture. Security administrators can use the output of an enumeration phase to build a comprehensive catalog of services and applications within the enterprise, enabling them to meet mandatory audit and regulatory requirements.
Risk assessment and management
When performing enumeration, security penetration testers uncover the risks posed by the application and the potential exploits that can be orchestrated over such vulnerabilities. Results of the enumeration process typically provide the security team with priorities to implement to keep the application secure. The outcomes of enumeration can also be used to design an incident response and management plan focusing on reducing the impact of an exploit in real time.
Helps to verify the effectiveness of security controls
Enumeration is a black-box attack technique that scans for common misconfigurations and weaknesses within a tech stack. External auditors and penetration testers rely on enumeration techniques to check for security gaps inadvertently missed by the development and security team during internal tests. As a result, the technique is often one of the recommended practices for teams who have recently made changes to standard services, applied security updates, or modified the user experience of an application.
Classification of Enumeration Techniques
Enumeration techniques are classified according to the information they are used to obtain and the targeted systems. Categories include:
Lightweight Directory Access Protocol (LDAP) Enumeration
The Lightweight Directory Access Protocol is an internet standard that facilitates access to distributed directory services. LDAP is tied to the DNS server for faster query resolution and lookups. In a lightweight directory access protocol enumeration, penetration testers use directory scanners to locate network file shares, current users, affiliated organizations, and other directory listings within the system. One common testing mechanism is to leverage a penetration scanning tool for querying TCP ports 389 and 636 to enumerate information such as valid usernames, organizational details, and addresses from LDAP servers.
The Network Basic Input Output System (NetBIOS) enables machines to communicate across the Local Area Network (LAN). As NetBIOS is responsible for assigning names to identify machines over a TCP/IP connection, a related enumeration enables the security team to obtain the list of computers within a domain, file shares on individual machines, organizational policies, and default passwords. This makes NetBIOS enumeration crucial for investigating security misconfigurations in sensitive accounts and shared resources.
Considered the principal reconnaissance technique for Windows operating systems, this involves the security team connecting with desktop workstations either locally or from a remote machine and then profiling the machine using sysinternals tools.
Information that can be obtained using Windows enumeration tools includes:
1. OS version
2. Firewall configuration
3. Directory structure
4. Most recent patches/updates
5. The machine’s domain
7. Device drivers
8. Device configuration
9. Running processes
10. Registry keys
11. Scheduled tasks
12. Cleartext password files
Although most enumeration processes are carried out using inbuilt utilities and commands, penetration testers can also use tools such as NMap, Metasploit, and rpcclient to obtain information on privileged accounts.
The Simple Network Management Protocol (SNMP) enables the exchange of management information between different network entities. The SNMP protocol tracks packets, errors and bytes transmitted, connection speed, and the number of requests to a web server. SNMP enumeration typically simulates an attack over SNMP agents of target devices, enabling security teams to gain unauthorized access to the Management Information Base (MIB) database containing network object records. This facilitates teams to identify devices, user accounts, passwords, client workgroups, and devices/system names within the network.
The Network Time Protocol (NTP) synchronizes clocks between computers over variable-latency, packet-switched networks. The protocol runs on a computer’s UDP port 123 and maintains a time synchronization of 10 milliseconds over the internet. NTP enumeration involves querying the NTP server for network information such as system names/IP addresses of hosts connected to the server and OS versions in the network’s clients. NTP enumeration also helps penetration testing teams to discover primary servers that allow system hosts to update their clocks without having to authenticate to the system.
Domain Name Service (DNS) servers run a redundant, distributed, hierarchical database containing internet domain names and IP tables. The DNS server hosts records detailing the types of resources in the network within the DNS zone files. The service relies on DNS zone transfer to replicate the database across servers.
DNS enumeration involves locating an organization’s DNS servers and client domain entries. Through DNS enumeration, security teams can obtain the list of vulnerable machines’ device names, domain controllers, usernames, and IP addresses. Penetration testers commonly use zone transfers to obtain DNS entries and IP addresses susceptible to being downloaded in human-readable ASCII text.
Does an enumeration attack offer attackers access to sensitive data?
Hackers mostly rely on enumeration as an information-gathering technique. They use enumeration techniques to uncover security gaps and remotely exploit vulnerabilities. Once an attacker enumerates a webserver and gains access to security configuration and active network connections, they can gain direct access to passwords and other sensitive information.
Why is account enumeration considered crucial in ethical hacking?
Account enumeration involves using the response of a failed authentication attempt to determine invalid and valid username entries. Account enumeration helps security teams verify the configuration of authentication controls while ensuring every defined security principle is upheld. With account enumeration, penetration testers can also check for the robustness of password policies, MFA, and other access controls to ensure the confidentiality of user activities/data.
Enumeration with Crashtest Security
Enumeration enables security teams to systematically collect details about network resources, security principles, and system vulnerabilities. For enhancing the overall security posture, the enumeration mechanism offers a comparative overview of administered security controls and flaws to be fixed.
Crashtest Security Suite offers a comprehensive, automated penetration testing platform with end-to-end vulnerability scanning for effective enumeration. The suite also generates extensive reports with actionable insights to help administer robust security controls for an application stack.
To know more about how Crashtest Security can be easily integrated with your existing workflow and help reduce security exposure, try a free 14-day trial here.
This article has already been published on https://crashtest-security.com/enumeration-phase/ and has been authorized by Crashtest Security for a republish.