A Remote Access Trojan (RAT) is a type of malware that enables an attacker to gain remote access over an infected system. Once a machine is compromised by a Remote Access Trojan, your system is at high risk of covert surveillance, data exfiltration, and other methods of malicious remote compromise.

This article defines what a Remote Access Trojan (RAT) is and how you can take action to protect your system with UpGuard BreachSight.

What is a Remote Access Trojan?

Like the name suggests, Remote Access Trojans provide remote access to malicious attackers. The name draws from the mythological Trojan Horse, which Virgil describes in the Aeneid as a wooden horse with attacking forces hidden inside. Those hidden attackers open the gates to the city of Troy during the night, allowing the rest of their army to enter and destroy the city.

Much like the mythological Trojan Horse after which it is named, Trojan horse malware will provide unauthorized access to the machine on which it is installed. This type of backdoor malware often spreads through social engineering, whether by a user downloading a file they believe to be safe but is actually malicious, such as an email attachment, fake software update, or malicious website pop-up. Some attackers make use of network endpoints to send a malicious payload into your system.

RAT attacks do not require physical access to the target system. Instead, threat actors compromise systems through remote access functionality.

How Does a Remote Access Trojan Work?

Remote access enables attackers to achieve unauthorized Remote Code Execution (RCE) and take advantage of your system without legitimate privileges. If a hacker gains access through a RAT and then performs RCE, they may be able to escalate their permissions to intrude further into your critical infrastructure or otherwise exploit existing vulnerabilities in your attack surface.

Once they have access, the attacker could leverage your authentication to perform cyberattacks against other unsuspecting victims. A Remote Access Trojan may be able to perform the following malicious activities on an infected machine:

  • Command and control server compromise
  • Log keystrokes and harvest credentials
  • Access files and folders for directory traversal
  • Take screenshots
  • Control the webcam and microphone
  • Retrieve sensitive information, such as personal identifiable information and credit card details
  • Install additional services or other forms of malware that compromise your system
  • Use your device as a proxy attacker against other systems
  • Run cryptocurrency mining from the victim's computer
  • Launch distributed denial-of-service (DDoS) attacks from the infected computer
  • Leverage your system's access to confidential services
  • Bypass intrusion detection systems and authentication controls

Some RAT attacks make isolated headway into your system, whereas others can gain full control over the target computer, including access to any administration tools.

If an attacker gains remote control of your machine through a RAT, your organization can be negatively impacted by these ensuing effects:

  • Confidential data loss
  • Privacy intrusion
  • Network compromise
  • Reputational damage
  • Use in proxy attacks

You can protect against RATs proactively with specific training and automated monitoring.

How to Protect Against Remote Access Trojans

Because Remote Access Trojans often access your device through surreptitious methods, it is critical that your security team trains all employees to be aware of social engineering techniques, such as phishing or unreliable attachments. Users should take caution with email attachments and internet downloads. Training employees to recognize their own user behaviors will help prevent attacker hijacking.

Consider whether a security gateway is necessary for your organization. A firewall or virtual private network (VPN) can provide additional layers of protection for data transfer. A zero-trust security framework provides a strong perimeter that can support protection against malware, but a Remote Access Trojan that gains entry through a device allowed inside the network can still wreak havoc.

When end-of-life software needs to be updated or migrated, ensure that any new software or patches are retrieved from a reliable and trusted source. Additionally, ensure that all employees upgrade their operating system with any official release, as updates at the operating system level often include security upgrades.

Run regular software assessments to ensure that spyware, keyloggers, and other malicious installations are not running on your devices. You can use an anti-malware solution to protect against some of these tools, but Remote Access Trojans are designed to avoid detection, so any use of anti-malware solutions can be paired with continuous monitoring against threat signals.

How UpGuard Can Help

In addition to preparing your team for social engineering attempts and creating security policies around downloads and updates, we recommend taking a proactive position to guard against potential cybersecurity threats. UpGuard BreachSight provides continuous monitoring and automated scanning for potential threats, including exposed ports that known RATs can exploit.

If you are at risk of exploitation due to a Remote Access Trojan, you will receive notification of open ports that may allow access to known RAT malware and botnets:

  • 'Ares RAT C&C' port open
  • 'Bozok RAT C&C' port open
  • 'DarkComet Trojan' port open
  • 'DarkTrack RAT' port open
  • 'Gh0st RAT' port open
  • 'KilerRAT C&C' port open
  • 'NanoCore RAT' port open
  • 'njRAT C&C' port open
  • 'Nuclear RAT' port open
  • 'Poison Ivy RAT' port open
  • 'Quasar RAT C&C' port open
  • 'RemCos Pro RAT' port open
  • 'Zero Access Trojan' port open

If you receive one of the identified RAT notifications, you will need to quarantine and investigate the affected asset to confirm if malware is present. Some common RAT behaviors include unexpected lag, antivirus software failure, unusual network traffic, keylogging, or an increase in unknown or unauthorized files on your device. Any suspicious activity warrants investigation to evaluate whether the cybercriminals have gained access through RAT attacks or other backdoors.

To find out if your organization is at risk of these RATs, log in and access your Risk Profile in BreachSight to search for the RAT findings. If you're not a current UpGuard user and you want to review your public-facing assets for these findings and more, sign up for a trial.

If you confirm that the asset has been contaminated by a Remote Access Trojan, you should quarantine the infected machine or compromised system immediately and follow your organization's incident response plan to disinfect the device and regain administrative control over the victim machine.

In addition to these known RATs, UpGuard scans for a wide variety of threat signals and services that could be running on your external attack service. To learn more about what services UpGuard scans, you can read the article on exposed services in the knowledge base.

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