Yaron Zinar

Find me on:

Recent Posts

Security Advisory: Targeting AD FS With External Brute-Force Attacks

Posted by Yaron Zinar on Jul 9, 2019 10:06:47 AM

On July 2019 Patch Tuesday, Microsoft released a patch for CVE-2019-1126, an important vulnerability discovered by Preempt Research Labs. The vulnerability discovered leads to security issues that create a wide scale denial-of-service against exposed organizations, and potentially, identity compromise.

While Microsoft only released one patch, we believe there are two vulnerabilities that allow attackers to remotely launch brute-force attacks on AD FS servers from the outside of the network. Attackers can bypass the Extranet Lockout Protection security feature and also bypass the Microsoft AD lockout policy(!) in certain scenarios. The implications vary between account compromise (due to weak passwords) or a massive denial-of-service to all domain accounts. All AD FS versions are vulnerable.

Read the press release

Read More

Topics: password brute force, Security Advisory, ADFS

How to Easily Bypass EPA to Compromise any Web Server that Supports Windows Integrated Authentication

Posted by Yaron Zinar on Jun 11, 2019 9:52:37 AM

As announced in our recent security advisory, Preempt researchers discovered how to bypass the Enhanced Protection for Authentication (EPA) mechanism to successfully launch NTLM relay attacks on any server that supports WIA (Windows Integrated Authentication) over TLS.

Read More

Topics: NTLM, Security Advisory, Microsoft

Security Advisory: Critical Vulnerabilities in NTLM Allow Remote Code Execution and Cloud Resources Compromise

Posted by Yaron Zinar on Jun 11, 2019 9:51:20 AM

On June 2019 Patch Tuesday, Microsoft released patches for CVE-2019-1040 and CVE-2019-1019, two vulnerabilities discovered by Preempt researchers. The critical vulnerabilities consist of three logical flaws in NTLM (Microsoft’s proprietary authentication protocol). Preempt researchers were able to bypass all major NTLM protection mechanisms.

Read More

Topics: NTLM, Security Advisory, Microsoft

New Microsoft Exchange Vulnerability Exposes Domain Admin Privileges: Here’s What to Do

Posted by Yaron Zinar on Feb 4, 2019 11:41:13 AM

Last week, the CERT Coordination Center (CERT/CC) issued a vulnerability note warning versions of Microsoft Exchange 2013 and newer are vulnerable to an NTLM relay attack that allows for attackers to gain domain admin privileges. Organizations that rely on Microsoft Exchange are currently at risk of a serious data breach. This attack is particularly concerning given that it obtains privileges to the domain controller, which is essentially the “keys to the kingdom.” We’ve simplified some of the specifics of this attack for the purposes of this blog, but for a full technical breakdown, please see research from Dirk-jan Mollema.

Read More

Topics: NTLM, Microsoft

Enterprises continue to suffer from poor password hygiene and a lack of visibility & control over privileged users

Posted by Yaron Zinar on Dec 19, 2018 6:08:06 AM

It has been more than a year since I last shared Preempt Inspector statistics. Last time we shared Preempt Inspector statistics we found some alarming numbers. With the end of 2018 approaching, I would like to share with you key findings from Preempt Inspector [a free security tool that has been replaced by the more robust and also free Preempt Lite] to help you focus on the most important security issues you might be facing.

Read More

Topics: Privileged Users, Insider Threats, Passwords, Stealthy Admin

The Security Risks of NTLM: Proceed with Caution

Posted by Yaron Zinar on Oct 18, 2018 10:50:00 AM

NTLM (NT LAN Manager) is Microsoft's old authentication protocol that was replaced with Kerberos starting Windows 2000. It was designed and implemented by Microsoft engineers for the purpose of authenticating accounts between Microsoft Windows machines and servers. Even though it has not been the default for Windows deployments for more than 17 years, it is still very much in use, and I have not yet seen a network where it has been completely abandoned. In fact, it also supported by the latest version of Active Directory.

Read More

Topics: Risk, Active Directory, NTLM, kerberos

Is Your PAM Solution Enough to Block Credential Theft?

Posted by Yaron Zinar on Sep 20, 2018 1:48:15 PM

I was recently working with a large US-based company that suffered from repeated breaches to their corporate network. After we deployed the Preempt Platform and started monitoring all traffic, we quickly found several hacked privileged accounts that attackers were using. The interesting thing was that all privileged accounts were protected with password vaults and their passwords were rotated every 24 hours. In that particular case, the attackers compromised a web gateway that some admins logged into each day using a plaintext password. Using this weakness, attackers easily defeated the Privileged Access Management (PAM) solution, they simply had to harvest the password each day and do whatever they wanted with it.

Read More

Disrupting the Cyber Kill Chain: How to Contain Use of Tools and Protocols

Posted by Yaron Zinar on Aug 17, 2018 1:59:37 PM

Preventing lateral movement and unauthorized domain access due to the misuse of network credentials - especially due to reconnaissance tools looking for weak spots - is a challenge plaguing many enterprises. In fact, it’s a decades-old security problem. A major issue for enterprises has been how to detect and contain the use of reconnaissance tools like BloodHound, authentication protocols such as NTLM, DCE/RPC, Kerberos and Lightweight Directory Access Protocol (LDAP), as well as other IT tools like PsExec and Powershell that are being misused or exploited by attackers.

Read More

Security Advisory: Critical Vulnerability in CredSSP Allows Remote Code Execution on Servers Through MS-RDP (Video)

Posted by Yaron Zinar on Mar 13, 2018 10:03:36 AM

In March Patch Tuesday, Microsoft released a patch for CVE-2018-0886, a vulnerability discovered by Preempt researchers. The vulnerability consists of a logical flaw in Credential Security Support Provider protocol (CredSSP) which is used by RDP (Remote Desktop Protocol) and Windows Remote Management (WinRM) that takes care of securely forwarding credentials to target servers. The vulnerability can be exploited by attackers by employing a man-in-the-middle attack to achieve the ability to run code remotely on previously not infected machines in the attacked network. The vulnerability, in many real-world scenarios where victim network has vulnerable network equipment, could result in an attacker gaining the ability to move laterally in the victim’s network and even infect domain controller with malicious software. No attacks have been detected in the wild by Preempt.

Read More

Topics: kerberos, Hacking, Threat Detection, Security Advisory, Microsoft, CredSSP

Lessons from Black Hat USA 2017: Defense in Depth

Posted by Yaron Zinar on Aug 18, 2017 4:19:49 PM

Last month I attended Black Hat USA 2017 conference. It did not disappoint. Overall the event and packed agenda was well worth it. I enjoyed the vibe, the networking, the briefings, the business hall and the wonderful keynote by Alex Stamos (I recommend you follow Eran’s post who shared some of Alex’s deep insights).  Overall the event covered a broad array of bleeding edge infosec topics with sessions on research, zero day exploits, open source tools, and other security risks and trends.  

Read More

Topics: big data, Black Hat, Lateral Movement