SMB Brute-Force
Detection overview
The "SMB Brute-Force" detection focuses on identifying attempts to gain unauthorized access to systems by brute-forcing credentials over the Server Message Block (SMB) protocol. SMB is widely used for network file sharing and resource access in Windows environments. Attackers often target SMB to obtain valid credentials, which can be used to move laterally within the network, escalate privileges, and access sensitive data.
The SMB (Server Message Block) Brute-Force detection is designed to identify and alert on potential malicious activities aimed at exploiting SMB services through repeated password guessing attempts.
Triggering Behavior: Excessive Authentication Attempts
SMB Brute-force detection is triggered by an internal host rapidly utilizing multiple accounts through the SMB protocol, notably for activities that involve file sharing or RPC.
This behavior is indicative of an attempt to ascertain the existence of accounts, potentially followed by password brute-forcing using common or default passwords.
Underlying Reasons for SMB Brute-force
This behavior may be caused by attackers trying to uncover usable account credentials within a network. These accounts can then be used to escalate privileges or move laterally within the system.
Alternatively, it could be a benign scenario where a host provides services through a portal, leading to multiple users logging in for services requiring an SMB connection.
Business Impact of SMB Brute-force
The primary risk from SMB brute-force attacks is the unauthorized discovery and exploitation of internal accounts, posing significant threats to data security and network integrity.
Such reconnaissance is often the precursor to more severe attacks, potentially leading to substantial data breaches or system disruptions.
Steps to Verify
To effectively investigate an SMB Brute-Force alert, follow these steps:
- Determine whether the internal host in question should be connecting to the target host using the indicated account(s); if not, this is likely malicious behavior
- Determine which process on the internal host is initiating the SMB requests; in Windows systems, this can be done using a combination of netstat and tasklist commands
- Verify that the process should be running on the internal host and whether the process is configured correctly
SMB Brute-Force
Possible root causes
Malicious Detection
- An attacker is using automated tools to brute-force SMB credentials to gain unauthorized access.
- Compromised systems within the network are being used to perform SMB brute-force attacks.
- Insider threat where an employee is attempting to access restricted SMB resources by brute-forcing credentials.
Benign Detection
- Legitimate users repeatedly trying to log in after forgetting their passwords.
- Security assessments or penetration tests involving controlled brute-force attack simulations.
- Misconfigured applications or systems causing repeated login attempts.
SMB Brute-Force
Example scenarios
Scenario 1: An attacker from an external IP address uses an automated tool to perform a brute-force attack on a company's SMB services, trying multiple usernames and common passwords. The detection is triggered by the high volume of failed login attempts from a single IP address.
Scenario 2: During a penetration test, the security team runs a controlled brute-force attack simulation on the organization's SMB services. The detection is triggered, and the activity is verified as part of the scheduled assessment.
SMB Brute-Force
Business impact
If this detection indicates a genuine threat, the organization faces significant risks:
Credential Compromise
Successful brute-force attacks can lead to unauthorized access to systems and sensitive data.
Lateral Movement
Attackers can use compromised credentials to move laterally within the network, escalating privileges.
Operational Disruption
Brute-force attacks can overwhelm authentication services, causing performance degradation and potential outages.
SMB Brute-Force
Steps to investigate
Review Authentication Logs
- Check logs for patterns of multiple failed login attempts to SMB services, including timestamps, source IP addresses, and usernames.
- Identify any successful login attempts following a series of failures.
Correlate with User Activity
- Verify if the affected accounts are associated with legitimate users who may have forgotten their passwords.
- Check for recent changes in user behavior, access patterns, or account privileges.
Examine Network Traffic
- Analyze network traffic for unusual patterns or spikes in SMB activity.
- Look for connections to known or suspicious IP addresses involved in brute-force attempts.
Conduct a Threat Hunt
- Search for other indicators of compromise or malicious activity associated with the same IP addresses or user accounts.
- Verify if the detected activity is part of a scheduled security assessment or penetration test.
FAQs
What is an SMB brute-force attack?
An SMB brute-force attack involves repeatedly attempting to guess the correct username and password for accessing SMB services, often using automated tools, until successful authentication is achieved.