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.
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.
Over the past few months, the Preempt research team discovered and reported two Microsoft NT LAN Manager (NTLM) vulnerabilities. These vulnerabilities have a common theme around two different protocols handling NTLM improperly. These issues are particularly significant as they can potentially allow an attacker to create new domain administrator accounts even when best-practice controls such as LDAP server signing and RDP restricted admin mode are enabled.
In a previous blog, we discussed the prevalence of weak passwords in the Enterprise. The fact of the matter is, once an attacker gains access to password challenges and exfiltrates them for offline cracking, they can crack them in most cases.