79 - Pentesting Finger

👉 Overview

👀 What ?

Pentesting Finger is a technique used in penetration testing to gather information about a system or network. It involves querying the 'Finger' protocol, a software tool that was originally used on UNIX-based systems to identify users and provide basic details about them.

🧐 Why ?

Pentesting Finger is important because it allows security testers to gather valuable information about users on a network, including their login name, phone number, and whether they are currently logged in. This information can be used to identify potential vulnerabilities or weak points in the system's security. Understanding and being able to use this technique is therefore crucial for both penetration testers and system administrators.

⛏️ How ?

To use Pentesting Finger, you would first need to identify a system that has the Finger service enabled. You can then use a terminal or command line interface to send a Finger query to the system, using the syntax 'finger @[hostname]'. The system will respond with a list of users and their associated information. It's important to note that the use of the Finger protocol is generally considered outdated and insecure, and most modern systems have it disabled by default.

⏳ When ?

The Finger protocol was first developed in the 1970s for use on UNIX-based systems. Pentesting Finger has been used since the advent of penetration testing as a field, but its usage has declined in recent years due to the inherent security risks of the Finger protocol.

⚙️ Technical Explanations

Pentesting Finger is a technique that leverages the Finger protocol to gather information about users on a network. This protocol, which operates on the application layer of the TCP/IP stack and listens on port 79, was originally developed in the 1970s for use on UNIX-based systems. It allows a user to query a system for a list of users and their associated details, such as their login name, phone number, and login status.

To utilize Pentesting Finger, a penetration tester first needs to identify a system with the Finger service enabled. This is typically done using a terminal or command line interface, sending a Finger query to the system using the syntax 'finger @[hostname]'. The system then responds with the requested user data.

However, the Finger protocol has significant security risks. The information it transmits is not encrypted, meaning it is sent in clear text over the network where it can be intercepted by malicious actors. This can provide them with sensitive information that can be exploited to breach the system's security.

Therefore, most modern systems have the Finger service disabled by default, and the use of the Finger protocol is generally considered outdated and insecure. Instead, more secure methods of user enumeration, such as LDAP or Kerberos, are recommended. Despite this, understanding the Finger protocol and its associated risks remains important for penetration testers and system administrators to help them identify and mitigate potential security vulnerabilities.

Let's consider an example where a penetration tester is trying to gather information about users on a UNIX-based system that has the Finger service enabled.

1. Identify the target system: The penetration tester identifies the target system. For our example, let's say the target system's hostname is targetsystem.com.
2. Send a Finger query: The tester will open a terminal or command line interface and send a Finger query to the targetsystem.com using the following command:

finger @targetsystem.com

1. Interpret the response: The system responds with a list of users and their associated details. An example response could look like this:

Login       Name               TTY        Idle    When    Where
user1       User One           pts/1      4:20    Mon 10:30  192.168.1.101
user2       User Two           pts/2      2:10    Mon 11:00  192.168.1.102

From this, the tester can learn the login names (user1, user2), their full names (User One, User Two), the terminal they're using (pts/1, pts/2), how long they've been idle (4:20, 2:10), when they logged in (Mon 10:30, Mon 11:00), and their IP addresses (192.168.1.101, 192.168.1.102).

1. Evaluate the security risks: The tester can see that the Finger protocol transmits this information in clear text over the network. This is a significant security risk as the information could be intercepted by malicious actors.

Remember that most modern systems have the Finger service disabled by default due to its significant security risks. More secure methods of user enumeration, such as LDAP or Kerberos, are typically used instead. However, understanding how to use and the risks associated with the Finger protocol is important for penetration testers and system administrators.