Pass the Hash (PtH) is a cybersecurity attack where an adversary captures a hashed user credential and uses it to authenticate and create a new session on the same network. Unlike other credential theft methods, PtH does not require the attacker to decrypt the password hash. Instead, the attacker leverages the stored hash to gain access, making it a particularly stealthy and effective technique.

This type of attack is especially prevalent on Windows systems, which use authentication protocols like NTLM and Kerberos. These protocols store password hashes in various locations, such as the Security Accounts Manager (SAM) and Local Security Authority Subsystem Service (LSASS). By exploiting these stored hashes, attackers can move laterally across the network, impersonating users and escalating their privileges without needing the actual passwords.

How does Pass the Hash Work?

Pass the Hash (PtH) attacks operate by exploiting the way authentication protocols handle password hashes. Initially, an attacker gains access to a network, often through social engineering techniques like phishing. Once inside, the attacker uses specialized tools to scrape active memory for password hashes. These tools, such as fgdump and pwdump7, extract the hashes from the Local Security Authority Subsystem Service (LSASS).

With the password hashes in hand, the attacker can authenticate themselves as the legitimate user without needing the actual password. This is possible because the authentication system treats the hash as a valid credential. The attacker then injects the hash into the authentication process, tricking the system into granting access. This allows the attacker to create new sessions and move laterally across the network, accessing different systems and applications.

As the attacker navigates through the network, they continue to harvest additional hashes from other systems. This enables them to escalate privileges and maintain persistent access. By leveraging these hashes, attackers can impersonate users, access sensitive data, and potentially deploy further malicious activities, all while remaining undetected.

What are Examples of Pass the Hash Attacks?

One notable example of a Pass the Hash (PtH) attack occurred in April 2022, involving the Hive ransomware-as-a-service (RaaS) platform. Attackers targeted Microsoft Exchange Server customers by exploiting a vulnerability known as ProxyShell. They planted a backdoor web script, ran malicious code, and used tools like Mimikatz to steal NTLM hashes. This allowed them to perform reconnaissance, collect data, and ultimately deploy the ransomware payload.

Another significant incident involved a financial services company where attackers leveraged PtH techniques to move laterally across the network. By capturing password hashes from the Local Security Authority Subsystem Service (LSASS), they gained unauthorized access to sensitive financial data. This breach not only compromised confidential information but also resulted in substantial financial losses and increased operational costs for the organization.

What are the Potential Risks of Pass the Hash?

• Compromise of Sensitive Information: Attackers can capture password hashes, which are considered sensitive information, and use them to gain unauthorized access to networked systems.

• Escalation of Privileges: Once inside the network, attackers can use the captured hashes to escalate their privileges, gaining higher levels of access and control over the network.

• Lateral Movement: Attackers can move laterally across the network, using the stolen hashes to access multiple systems and potentially compromise more data and resources.

• Disruption of Business Operations: Pass-the-hash attacks can lead to increased operational costs and resource allocation to address the attack, disrupting normal business activities.

• Financial Losses: Organizations may suffer significant financial losses due to lost revenue and the costs associated with mitigating the attack and recovering from its impact.

How can you Protect Against Pass the Hash?

Protecting against Pass the Hash (PtH) attacks requires a multi-faceted approach. Here are some key strategies:

• Implement Multi-Factor Authentication (MFA): Adding an extra layer of security makes it harder for attackers to gain access even if they have the password hash.

• Enforce the Principle of Least Privilege (POLP): Limit user access rights to only what is necessary for their job functions, reducing the potential impact of a compromised account.

• Use Privileged Access Management (PAM): Secure privileged accounts by rotating passwords frequently and using one-time passwords (OTPs).

• Enable Endpoint Protection: Utilize tools like Microsoft Windows Defender Credential Guard (WDCG) to isolate and protect sensitive data from unauthorized access.

• Conduct Regular Security Audits: Regularly review and update security policies, and perform penetration testing to identify and mitigate vulnerabilities.