Adversaries with no prior knowledge of legitimate credentials within the system or environment may guess passwords to attempt access to accounts. Without knowledge of the password for an account, an adversary may opt to systematically guess the password using a repetitive or iterative mechanism. An adversary may guess login credentials without prior knowledge of system or environment passwords during an operation by using a list of common passwords. Password guessing may or may not take into account the target's policies on password complexity or use policies that may lock accounts out after a number of failed attempts. Guessing passwords can be a risky option because it could cause numerous authentication failures and account lockouts, depending on the organization's login failure policies. (Citation: Cylance Cleaver) Typically, management services over commonly used ports are used when guessing passwords. Commonly targeted services include the following: * SSH (22/TCP) * Telnet (23/TCP) * FTP (21/TCP) * NetBIOS / SMB / Samba (139/TCP & 445/TCP) * LDAP (389/TCP) * Kerberos (88/TCP) * RDP / Terminal Services (3389/TCP) * HTTP/HTTP Management Services (80/TCP & 443/TCP) * MSSQL (1433/TCP) * Oracle (1521/TCP) * MySQL (3306/TCP) * VNC (5900/TCP) * SNMP (161/UDP and 162/TCP/UDP) In addition to management services, adversaries may "target single sign-on (SSO) and cloud-based applications utilizing federated authentication protocols," as well as externally facing email applications, such as Office 365.(Citation: US-CERT TA18-068A 2018). Further, adversaries may abuse network device interfaces (such as `wlanAPI`) to brute force accessible wifi-router(s) via wireless authentication protocols.(Citation: Trend Micro Emotet 2020) In default environments, LDAP and Kerberos connection attempts are less likely to trigger events over SMB, which creates Windows "logon failure" event ID 4625.

Linked Issues

Issuelinks
Linktype Issue
is related to Techniques
is blocked by Update Software
is blocked by Password Guessing via Multi-Source Authentication Failure Correlation
is blocked by Multi-factor Authentication
is blocked by Password Policies
is blocked by Account Use Policies
is blocked by Security, Compliance & Resilience Controls Oversight
is blocked by Secure Baseline Configurations
is blocked by Continuous Monitoring
is blocked by Use of External Technology Assets, Applications and/or Services (TAAS)
is blocked by Separation of Duties (SoD)
is blocked by Identification & Authentication for Organizational Users
is blocked by Identifier Management (User Names)
is blocked by Authenticator Management
is blocked by Re-Authentication
is blocked by Account Management
is blocked by Access Enforcement
is blocked by Least Privilege
is blocked by Account Lockout
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