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Risks & Dangers of Remote Access
Avast and NordVPN, on the same day last October 21st, disclosed a separate and unrelated unauthorized intrusion into their respective networks. While these network intrusions were unrelated, these intrusions were a result of a common cyber security weakness: remote access.
What Is Remote Access?
Remote access allows a user to access a computer or a network, despite the fact that the user has no physical access to said computer or private network. Remote access to a private network can be achieved through virtual private network (VPN) or a remote access feature of an operating system.
An example of a remote access feature of an operating system is the remote desktop protocol (RDP). In Windows operating systems, RDP allows network administrators to manage or troubleshoot computers over the internet.
VPN service providers, meanwhile, promise to offer secure and encrypted connections to its customers. In both VPN and RDP, access to private network is conducted from a remote location using a laptop, desktop computer or mobile device connected to the internet.
Unauthorized Remote Access on Avast Network
Last October 21st, Avast, in a statement, said that on September 23 of this year, it identified suspicious activity on its network. After further analysis, Avast said it found that its internal network was successfully accessed with compromised credentials through a temporary VPN profile that had erroneously been kept enabled and didn’t require 2-factor authentication (2FA).
Avast said that the malicious actor had been attempting to gain access to the company’s network through its VPN as early as May 14 of this year. The company said it closed the temporary VPN profile that was accessed by a malicious actor.
As a precaution, the company suspended the upcoming releases of its product CCleaner and started checking prior CCleaner releases and verified whether malicious alterations had been made. As an added precaution, the company also re-signed a clean update of the product and provided it to users through an automatic update last October 15th.
Avast admitted in September 2017 that its product CCleaner, which it acquired from Piriform on July 18, 2017, had been compromised by malicious actors, resulting in the downloads of 2.27 million of the corrupt CCleaner version by unknowing customers.
Unauthorized Remote Access on NordVPN Network
Last October 21st, virtual private network service provider NordVPN admitted that in March 2018, one of its servers, which the company rented with a third party data center in Finland, was accessed without authority.
NordVPN said that the attacker gained access to the server by exploiting an “insecure” remote management system left by the data center provider. The virtual private network service provider said it had no knowledge the data center provider was using the remote management system.
NordVPN said it immediately terminated the contract with the third party data center and destroyed all servers that the company had been renting from the data center. The virtual private network service provider said that TLS key was taken at the same time the data center was exploited.
The company said that no user credentials have been intercepted. It also said that the TLS key “couldn’t possibly have been used to decrypt the VPN traffic of any other server.” NordVPN said that “the only possible way to abuse website traffic was by performing a personalized and complicated MiTM [man-in-the-middle] attack to intercept a single connection that tried to access nordvpn.com”.
In a man-in-the-middle attack, the attacker intercepts user traffic to steal credentials and other important information. The attacker then uses this stolen information to access the actual destination network. Preventing man-in-the-middle attacks is the reason why people use VPN in the first place.
"Intercepting TLS traffic isn't as hard as they make it seem," security researcher who uses the name “hexdefined”, one of those who analyzed the data exposed in the NordVPN breach, told Ars Technica. "There are tools to do it, and I was able to set up a Web server using their TLS key with two lines of configuration. The attacker would need to be able to intercept the victim's traffic (e.g. on public Wi-Fi)."
Preventive and Mitigating Measures
While remote management systems such as RDP and VPN have a number of benefits, their inherent weakness shouldn’t be ignored, that is, these systems provide a door to your organization’s network to the public internet. These remote management systems or these doors should be closed and opened only to authorized personnel.
One of the preventive measures in protecting these remote management systems from unauthorized entry is through the use of multi-factor authentication or 2-factor authentication. As shown in the case of the Avast data breach, using a VPN account without 2-factor authentication attracts malicious actors.
It’s important to note that there are currently tools to bypass 2-factor authentication or multi-factor authentication. For instance, security researchers at DEVCORE disclosed that they were to access the internal network of Twitter by bypassing the 2-factor authentication for the VPN used by Twitter. While the use of multi-factor authentication or 2-factor authentication isn’t the cure-all in protecting your organization’s network, this security measure decreases a number of attack surfaces.
Network segmentation, the practice of splitting your organization’s network into subnetworks, is another cyber security measures to block malicious actors. This practice ensures that if one network is breached, the others won’t be affected.
It’s also ideal not to install or disable remote management systems on the servers that housed your organization’s critical data in order not to expose this data to the public domain.
Steve E. Driz, I.S.P., ITCP