|Platform||Linux, macOS, Windows|
|Data Sources||Authentication logs|
Adversaries may use brute force techniques to attempt access to accounts when passwords are unknown or when password hashes are obtained.
Credential Dumping to obtain password hashes may only get an adversary so far when Pass the Hash is not an option. Techniques to systematically guess the passwords used to compute hashes are available, or the adversary may use a pre-computed rainbow table. Cracking hashes is usually done on adversary-controlled systems outside of the target network.1
Adversaries may attempt to brute force logins without knowledge of passwords or hashes during an operation either with zero knowledge or by attempting a list of known or possible passwords. This is a riskier option because it could cause numerous authentication failures and account lockouts, depending on the organization's login failure policies.2
A related technique called password spraying uses one password, or a small list of passwords, that matches the complexity policy of the domain and may be a commonly used password. Logins are attempted with that password and many different accounts on a network to avoid account lockouts that would normally occur when brute forcing a single account with many passwords.3
- APT3 has been known to brute force password hashes to be able to leverage plain text credentials.4
- APT34 has used brute force techniques to obtain credentials.5
- Dragonfly dropped and executed Hydra, a password cracker.67
- Lazarus Group malware attempts to connect to Windows shares for lateral movement by using a generated list of usernames, which center around permutations of the username Administrator, and weak passwords.8
- Turla may attempt to connect to systems within a victim's network using
net usecommands and a predefined list or collection of passwords.9
- Chaos Chaos conducts brute force attacks against SSH services to gain initial access. 10
- Net Crawler uses a list of known credentials gathered through credential dumping to guess passwords to accounts as it spreads throughout a network.2
Set account lockout policies after a certain number of failed login attempts to prevent passwords from being guessed. Use multifactor authentication. Follow best practices for mitigating access to Valid Accounts
It is difficult to detect when hashes are cracked, since this is generally done outside the scope of the target network.
Monitor authentication logs for system and application login failures of Valid Accounts. If authentication failures are high, then there may be a brute force attempt to gain access to a system using legitimate credentials.
Also monitor for many failed authentication attempts across various accounts that may result from password spraying attempts.
- Wikipedia. (n.d.). Password cracking. Retrieved December 23, 2015.
- Cylance. (2014, December). Operation Cleaver. Retrieved September 14, 2017.
- Thyer, J. (2015, October 30). Password Spraying & Other Fun with RPCCLIENT. Retrieved April 25, 2017.
- Korban, C, et al. (2017, September). APT3 Adversary Emulation Plan. Retrieved January 16, 2018. |
- Davis, S. and Caban, D. (2017, December 19). APT34 - New Targeted Attack in the Middle East. Retrieved December 20, 2017.
- US-CERT. (2017, October 20). Alert (TA17-293A): Advanced Persistent Threat Activity Targeting Energy and Other Critical Infrastructure Sectors. Retrieved November 2, 2017.
- Kali. (2014, February 18). THC-Hydra. Retrieved November 2, 2017.
- Novetta Threat Research Group. (2016, February 24). Operation Blockbuster: Remote Administration Tools & Content Staging Malware Report. Retrieved March 16, 2016.
- Kaspersky Lab's Global Research and Analysis Team. (2014, August 7). The Epic Turla Operation: Solving some of the mysteries of Snake/Uroburos. Retrieved December 11, 2014.
- Sebastian Feldmann. (2018, February 14). Chaos: a Stolen Backdoor Rising Again. Retrieved March 5, 2018.