Canadian Centre for Cyber Security Warns About the Continued Exploitation of Multiple Vulnerabilities

Canadian Centre for Cyber Security Warns About the Continued Exploitation of Multiple Vulnerabilities 

The Government of Canada, through the Canadian Centre for Cyber Security, has warned that threat actors are exploiting multiple known vulnerabilities present in information systems in Canada.

According to the Canadian Centre for Cyber Security (Cyber Centre), as information systems and the networks linking them are critical components in today’s interconnected world and relied upon by governments, small businesses and individuals worldwide, the need to secure them is of utmost importance. The Cyber Centre’s warning is similar to the U.S. Government’s warning, through the National Security Agency (NSA), that threat actors are targeting U.S. information systems such as unpatched remote access services, security appliances and application servers.

"The Cyber Centre continues to receive reports of persistent exploitation of known vulnerabilities," the Cyber Centre said. “While manufacturers work hard to provide updates for vulnerabilities, these updates are not always applied in a timely manner by consumers.”

Target Vulnerabilities

Among the vulnerabilities that are being actively exploited by threat actors according to the Cyber Centre and NSA are the following:

Microsoft Netlogon Elevation of Privilege Vulnerability

This vulnerability, designated as CVE-2020-1472 and commonly known as ZeroLogon, is described by Microsoft as an elevation of privilege vulnerability that exists when an attacker establishes a vulnerable Netlogon secure channel connection to a domain controller using the Netlogon Remote Protocol (MS-NRPC) – Microsoft Windows’ core authentication component of Active Directory that provides authentication for user and computer accounts.

“By simply sending a number of Netlogon messages in which various fields are filled with zeroes, an attacker can change the computer password of the domain controller that is stored in the AD [Active Directory],” Tom Tervoort, Senior Security Specialist at Secura and the one who discovered the Netlogon vulnerability, said in the whitepaper “ZeroLogon: Unauthenticated domain controller compromise by subverting Netlogon cryptography (CVE-2020-1472).” “It basically allows any attacker on the local network (such as a malicious insider or someone who simply plugged in a device to an on-premise network port) to completely compromise the Windows domain.”

Remote Code Execution Vulnerability Affecting Citrix Application Delivery Controller (ADC)

ADC is described by Citrix as a networking appliance whose function is to “improve the performance, security and resiliency of applications delivered over the web.” Designated as CVE-2019-19781, this security vulnerability in Citrix ADC, if exploited, could allow an unauthenticated attacker to perform remote code execution – the ability of an attacker to access or make changes to another computer, regardless of where the attacker’s computer is geographically located.

In July of this year, the Canadian Centre for Cyber Security reported that several computer networks in Canada were compromised and, in each case, a threat actor was able to compromise infrastructure exposed to the internet because the software running on an exposed server wasn’t patched to the latest version or properly secured via two-factor authentication. According to the Cyber Centre, prior to the successful compromise of vulnerable and improperly secured servers and network access devices, intensive reconnaissance-style scanning of target networks is often conducted by malicious actors. In some cases, malicious software (malware) was installed and compromised infrastructure may have been used in attempts to compromise other networks and/or other organizations.

Cybersecurity Best Practices

While it’s important to keep all software and firmware up to date, this alone isn’t the whole solution in keeping your organization safe from attackers.

Rare Cases of Multiple Patches

Microsoft is addressing the CVE-2020-1472 vulnerability via a two-part patch rollout. The first patch was released on August 11, 2020 and the last patch will be released in the first quarter of 2021.

What should be done before the arrival of the second part of the patch? Aside from applying the August 11th patch, according to Microsoft, the following steps should be taken:

1. (a) Monitor for warning events and (b) act on each event.
2. (a) Once all warning events have been addressed, full protection can be enabled by deploying DC enforcement mode. (b) All warnings should be resolved before the February 9, 2021 enforcement phase update.

False Sense of Security

It’s important to note that patching alone doesn’t fix a successful network compromise conducted via vulnerability exploitation. For instance, applying the patch for CVE-2019-19781 vulnerability, released by Citrix in January 2020, isn’t enough to fix a network compromised via CVE-2019-19781 exploitation.

In July 2020, Fox-IT reported that back in January 2020, just a few days after the release of the CVE-2019-19781 patch, a total of 1,030 compromised servers were identified, including those owned by Governmental organizations and Fortune 500 companies.

“However, of perhaps more concern was that, of these compromised devices, 54% had been patched against CVE-2019-19781, thus providing their administrators with a false sense of security,” Fox-IT said. “This is because although the devices were indeed patched, any backdoor installed by an attacker prior to this would not have been removed by simply installing the vendor’s patch.”

CVE-2019-19781 also showcased how attackers compete to remain in the networks that they’ve compromised, also known as "hacker turf war." Some threat actors applied the CVE-2019-19781 patch themselves to block other threat actors in what is known as “adversary patching.”

If for some reason your organization has failed to apply a critical patch in a timely manner, expect that credentials, accounts and software have been changed prior to the application of the patch and expect that patching won't alleviate the situation.