Forensic: nmap smb-enum-users.nse attack (en)

Nmap smb-enum-users.nse is a script used to enumerate users on Windows systems with active SMB (Server Message Block) services. This script employs two main methods:

• SAMR enumeration: This method is subtler and requires fewer packets for each user account. However, the information obtained may not be as complete as that from the LSA method.
• LSA bruteforcing: This method is noisier, generating more network traffic and log entries. However, it can provide more comprehensive information about user accounts.

Example Attack

Suppose we want to enumerate users on a Windows server named "server-windows" that can be accessed from our network. We can run the following Nmap commands:

wget https://svn.nmap.org/nmap/scripts/smb-enum-users.nse

nmap -sV --script smb-enum-users.nse server-windows
nmap --script smb-enum-users.nse -p445 <host>
sudo nmap -sU -sS --script smb-enum-users.nse -p U:137,T:139 <host>

Options used:

• `-sV`: Performs version scanning to obtain service version information.
• `--script smb-enum-users.nse`: Runs the smb-enum-users.nse script.

Expected Results

The output from the above commands will display a list of users found on the Windows server, including usernames, SIDs (Security Identifiers), and other information.

Attack Forensics

If we find evidence of an attack using smb-enum-users.nse, some artifacts we can look for include:

1. Nmap Logs: If the attacker ran Nmap from an accessible system, we can check Nmap logs to find the commands used.
2. System Logs: Examine the logs on the target Windows server for suspicious activity, such as failed login attempts or unusual network activity.
3. Firewall Logs: If there’s a firewall protecting the server, check the firewall logs for suspicious traffic from the attacker’s IP address.
4. Network Traffic Capture: If we have captured network traffic, we can analyze it for packets related to the smb-enum-users.nse attack.
5. Windows Event Logs: Check the event log on the Windows server for entries related to user enumeration attempts.

Mitigation

To prevent smb-enum-users.nse attacks, several measures can be taken:

• Disable Unnecessary SMB: If SMB is not needed, disable the SMB service on the server.
• Restrict Network Access: Limit network access to the server to authorized users only.
• Use a Firewall: Configure the firewall to block unauthorized traffic.
• Update Operating Systems and Applications: Ensure that the operating system and applications are always updated with the latest security patches.
• Use Strong Passwords: Enforce users to use strong and unique passwords for each account.
• Enable Audit Logging: Activate audit logging features to track user and system activity.

Important to Remember

• Educational Purpose: The above explanation is solely for educational and research purposes. Do not use this information for illegal activities.
• Laboratory Environment: It’s advisable to conduct these tests in an isolated laboratory environment to avoid unintended consequences.
• Permission: Always obtain necessary permissions before testing systems that are not owned by you.

Interesting Links

• Forensic: IT
• SMB (Server Message Block): Learn in-depth about the SMB protocol, including how it works and common vulnerabilities.
• Nmap: Explore various features and options of Nmap that can be used for scanning and exploitation.
• Network Forensics: Study how to analyze network traffic to find evidence of suspicious activity.
• Windows Forensics: Learn how to analyze Windows systems to uncover evidence of cybercrime.