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An Overview Of Pass-The-Hash In Cybersecurity

By Tom Seest

What Is Pass-The-Hash In Cybersecurity?

Pass-the-hash is a credential theft and lateral movement technique that takes advantage of the challenge-response model of NTLM authentication in Windows networks.
Pass-the-hash is distinct from other credential theft attacks in that it doesn’t require a user’s password to be stolen or decrypted; rather, it relies on a stored hash of their credentials.
PtH attacks can be one of the most challenging to stop. But with a few key measures in place, you can drastically reduce their potential impact on your organization.

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What Is Pass-The-Hash?

Pass-the-hash is a hacking technique that enables an attacker to authenticate as a user without ever having access to their cleartext password. This method is commonly employed for credential theft and lateral movement within organizations’ networks, circumventing normal system access controls.
Pass-the-hash attacks (PtHs) are common in Windows networks, where the challenge-response model of NTLM authentication can be exploited to grant attackers access to systems. Even though Kerberos has replaced NTLM as the primary authentication protocol in many domains, PtHs remain a popular way for cybercriminals to take control of accounts and obtain higher privileges.
Pass-the-hash attacks involve attackers using various tools to harvest hashed passwords from a targeted computer. Once harvested, these hashes are stored in memory and used again for creating a new authenticated session.
Once an attacker logs in, they have the ability to move laterally between different machines and account types in the network. Furthermore, they can extract additional information and credential sets which they can use for elevating their privileges or performing other malicious activities.
These attacks are typically used as a prelude to more sophisticated techniques like file exfiltration and malware infection. In April 2022, Hive, a ransomware-as-a-service (RaaS) platform, employed a pass-the-hash exploit in order to launch a coordinated attack that targeted Microsoft Exchange Server customers in energy, financial services, nonprofit and healthcare sectors.
The attack relied on a Windows security vulnerability that allowed attackers to steal password hashes, which they then used to circumvent authentication protocols and log on to systems. Fortunately, Microsoft has since patched this issue, meaning organizations no longer face an immediate risk from this flaw.
The best defense against pass-the-hash attacks is to secure network-privileged access. This necessitates strong passwords, effective user account management practices, and a security strategy that monitors all aspects of privileged activity on your network. This includes monitoring login and password logs for suspicious activity as well as looking into other system events which could indicate a PtH attack.

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How Do Pass-The-Hash Attacks Work In Cybersecurity?

Pass-the-Hash attacks are a popular technique used by attackers to gain access to user passwords. This technique works because hashed passwords cannot be cracked back to their original form, making them ideal targets for this attack.
When you log in to a computer, the operating system stores your password as a hash. This helps verify your identity when accessing services or systems over the network.
This makes it more difficult for malicious individuals to gain access to your credentials and use them for malicious activities. Furthermore, this keeps your data safe from phishing attacks and other security flaws.
However, this mechanism may not be perfect. It may not be able to protect you against all phishing attempts, malware infections, and other cyber threats; therefore, taking precautions is key for safeguarding your network and users.
One of the most effective methods for protecting against these attacks is by restricting lateral movement with attack path management. Doing this will stop attackers from quickly moving from server to server.
Additionally, it is imperative to remove unnecessary administrative rights from your servers and workstations. Doing this will reduce the potential damage of a Pass-the-Hash attack.
In addition to these measures, it is essential that your users remain up-to-date on the most recent security patches and anti-malware software. Doing this will guarantee your systems remain shielded against exploits and other potential threats.
Furthermore, you should keep an eye on your login activity and alerts so that any suspicious activities can be identified. Doing this will reduce the number of successful login attempts as well as other security risks which could lead to an attack such as pass-the-hash.
Additionally, ensure all machines in your network are firewalled to prevent peer-to-peer subnet jumps from one host to another. Doing this can guard against pass-the-hash attacks caused by worms and other forms of malware.
Fortunately, there are several tools that can detect pass-the-hash attacks and alert you of any issues. These include programs that audit logon activity and alert you of failed logins or other potential infiltration attempts into your network.

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What Are the Countermeasures to Pass-The-Hash Attacks In Cybersecurity?

Pass the hash (PTH) attacks are a commonly employed online exploit by cyber criminals. According to the US Computer Emergency Readiness Team, SANS Institute, and McAfee, credential theft through PTH attacks poses an immediate and serious threat to cybersecurity.
In many cases, this type of attack relies on an attacker scraping active memory for NTLM hashes. Once these hashes are in their possession, they can use them to trick an authentication system into creating a new authenticated session on the network.
Therefore, cybercriminals can easily roam the network without detection and gain access to valuable systems that have been compromised. This includes critical servers, data, and other digital assets essential to running a business.
Fortunately, there are a few countermeasures security teams can use to defend against these attacks. These include specialized solutions, system hardening policies, and monitoring suspicious login behavior.
Another effective way to protect against pass-the-hash attacks is network segmentation. By segregating workstations and servers, hackers cannot move laterally between devices and accounts. This helps limit the damage caused by PTH-style attacks by denying them full access to critical systems within your organization.
Finally, identity segmentation can protect against pass-the-hash attacks by restricting user access to resources based on their identities. This is an integral element of an effective identity-based security strategy and often pairs with strong password policies with frequent account changes.
Identity segmentation not only reduces the risk of pass-the-hash attacks, but it can also protect organizations’ networks and IT infrastructure against malware, ransomware, and other threats. For instance, creating a separate domain and file server for each department or division helps prevent lateral movement between departments and guarantees privileged accounts aren’t vulnerable to pass-the-hash attacks.
While these countermeasures can help guard against pass-the-hash attacks, they won’t be enough to safeguard your organization against live, advanced, and persistent attackers. You need a comprehensive strategy that addresses all aspects of your security posture in order to combat these risks effectively.

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How to Mitigate Pass-The-Hash Attacks In Cybersecurity?

Pass-the-hash attacks are a type of credential theft-and-reuse attack that enables cybercriminals to move between devices and accounts in an IT environment. Cybercriminals typically start with a basic user account which they can purchase stolen credentials off the dark web or infect with password-stealing malware on a network device.
Once hackers have obtained a low-level user’s password, they use it to log into the system and begin looking for ways to elevate their domain privileges. They do this by logging into different systems using their compromised account as authentication, giving them access to more influential systems like an administrator account on their personal computer.
One of the best ways to protect against pass-the-hash attacks is by adding additional protection and monitoring to critical accounts and assets in your organization. This may include granting admin rights only to domain controllers, taking away all privileges from local administrators, and restricting access to shared resources that are utilized by many people within your company.
This will reduce the value of accounts that have been compromised and protect any data they may access. Furthermore, it’s essential to monitor user activity by analyzing their logon patterns and network traffic production.
Another way to protect against pass-the-hash attacks is to train your employees on recognizing and avoiding phishing emails or other social engineering techniques. Doing this will guarantee that employees do not unwittingly provide attackers with the initial set of credentials necessary for successful lateral movement.
Finally, ensure to regularly upgrade your cybersecurity tools and software in order to stay up-to-date. Doing this can help guard against any vulnerabilities in software that could allow cybercriminal access to your network.
You can implement technologies that ingest, parse, and analyze Windows Event Logs, EDR logs, Kerberos logs, and Active Directory information to detect potential signs of a PtH attack. This data will be invaluable in determining where the threat actor has gained access to your IT environment, what credentials they may have acquired, and what data they may have taken.

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