If you’re wondering what is a Remote Access Trojan (RAT), we’ve got you covered.
Attackers use these powerful tools to gain unauthorized remote access and control over a victim's system, posing significant security threats. So, it’s important to understand what they are, how they’re used, and how to defend against them.
In this article, we’ll explain everything you need to know about RATs, including what they are, how they work, and their dangers.
We’ll show you real-world examples and how you can detect them on your system, and finally, how they can be used for good as part of ethical hacking or a red team exercise.
Are you ready to explore the world of RAT malware? Let’s begin.
What Is a Remote Access Trojan (RAT)?
A remote access trojan (RAT) is a type of malware in the trojan horse family that allows an unauthorized user (black hat hacker, threat actor, etc.) to access another system, such as a desktop, laptop, or mobile device.
As the name suggests, one characteristic distinguishing a remote access trojan from other attacks in the same family is that it’s remotely controlled, meaning it could come from halfway across the world.
Other characteristics include its ability to execute commands, download and upload files, and modify system settings. It’s also persistent. In fact, RATs are often designed to hide from antiviruses and can maintain access even after system reboots.
It can also give the attacker backdoor access to the system at any time, and certain kinds may also be able to spread to other devices on the same network.
Difference Between Remote Access Tools and Malicious RATs
Most RATs are considered malicious software, giving the threat actor unauthorized system control.
However, there are instances where an authorized user may employ a RAT-like tool for legitimate purposes. In such cases, this type of software is referred to as a remote access tool rather than a trojan.
Remote access tools are legitimate software designed to provide authorized remote access to systems. IT professionals, support teams, and remote workers often use them to perform tasks like troubleshooting, maintenance, and accessing systems from remote locations.
Examples of legitimate remote access tools include:
- TeamViewer: A widely used tool for remote support and meetings
- AnyDesk: Known for its high-performance remote desktop capabilities
- Remote Desktop Protocol (RDP): Built into Windows for remote management
How RATs Work
In this section, we’ll discuss how RATs work. We’ll give you an overview of the RAT's lifecycle and a breakdown of each stage.
1. Infection Vectors
The first stage in the lifecycle of RAT software involves how it infects the target system. Common infection vectors include:
- Phishing Emails
- Malicious Downloads
- Drive-By Downloads
- Exploiting Vulnerabilities
- Social Engineering
2. Installation and Persistence
Once the RAT is delivered to the system, it goes through the installation and persistence stage to maintain control over the system.
Installation
The RAT payload is executed, often through an initial dropper that downloads the full RAT. It then modifies system settings, registry entries, or other configuration files.
Persistence
The RAT configures itself to run on startup by modifying registry keys, creating scheduled tasks, or placing itself in startup folders. Some RATs even install rootkits to hide their presence and avoid writing files to disk, operating from memory to evade detection.
3. Command and Control (C2) Infrastructure
The RAT must communicate with the attacker’s command and control (C2) server to receive instructions and send back data.
RATs connect to one or more C2 servers the attacker controls to receive commands and report back. Common protocols include HTTP, HTTPS, DNS, and custom TCP/UDP protocols.
Some RATs use encrypted channels to secure communication and may use dynamic DNS or a list of backup C2 servers to avoid detection and ensure constant communication.
4. Data Exfiltration and Remote Control
After connecting to the C2 server, the RAT enters the active phase and performs various activities.
Data Exfiltration
The RAT collects sensitive data such as login credentials, personal information, financial data, and other valuable information. It can download specific files or entire directories to the C2 server, recording keystrokes to capture passwords, messages, and other typed information. It also takes screenshots or records the screen.
Remote Control
The attacker can execute arbitrary commands on the infected system, including downloading/uploading files, starting/stopping processes, modifying system settings, and remotely controlling peripheral devices like webcams and microphones. The RAT may also attempt to spread to other devices on the same network, increasing the attack surface.

The Dangers of Remote Access Trojans
Remote access trojans pose significant dangers due to their ability to access and control systems unauthorizedly. Here are some of the key risks associated with RATs.
1. Data Theft
RATs can steal sensitive personal information, including login credentials and financial data. In a corporate environment, RATs can exfiltrate sensitive business information, trade secrets, and intellectual property.
2. Surveillance and Espionage
RATs can log keystrokes to capture passwords for online accounts and other typed information. They can take screenshots or record videos of the user’s activities, capturing sensitive information displayed on the screen. RATs can activate the webcam and microphone to spy on the user, capturing private conversations and images.
3. System and Network Manipulation
RATs allow attackers to gain remote control over the infected computer, allowing them to perform any action the user can, including installing software, deleting files, and modifying system settings. RATs can spread to other devices on the same network, increasing the scope of the attack and even compromising an entire network of devices.
4. Financial Loss
RATs can steal money directly by logging into banking websites and transferring funds. Attackers can also use RATs to deploy ransomware, encrypting the victim's data and demanding a ransom for release. Stolen credentials can be used for fraudulent transactions, leading to financial loss for individuals and businesses.
5. Identity Theft
Stolen personal information can be used to impersonate the victim, leading to various forms of identity theft. In business, attackers can use stolen corporate information to impersonate executives or employees, leading to further attacks such as the Business Email Compromise (BEC).
6. Damage to Reputation
Sensitive personal information, including private communications and images, can be leaked or misused, damaging the victim's reputation. Data breaches resulting from RAT infections can damage a company’s reputation, leading to loss of customer trust and potential legal liabilities.
7. Legal and Compliance Issues
Unauthorized data access and breaches can lead to non-compliance with data protection regulations such as GDPR, CCPA, and HIPAA, resulting in hefty fines and legal penalties. Victims of RAT attacks may face legal actions from affected parties whose data has been compromised.
8. Extended Attack Surface
RATs can open backdoors for additional malware, allowing attackers to execute further attacks, such as DDoS attacks, or launch other types of malware. Infected devices can be added to botnets, networks of compromised devices that carry out large-scale attacks, such as spam campaigns.
Real-World Consequences
Here are some real-world incidents involving remote access trojans that highlight the severe consequences of these attacks.
Operation Shady RAT
Operation Shady RAT was a large-scale cyber-espionage campaign discovered by McAfee in 2011. The attack involved using a RAT to infiltrate over 70 global organizations, including governments, corporations, and non-profit organizations.
Massive amounts of sensitive data, including government secrets and corporate intellectual property, were stolen. The theft of proprietary information led to significant financial losses for the affected companies.
DarkComet RAT
DarkComet is a well-known RAT used in various cyber attacks. In 2012, it was used in attacks targeting Syrian activists during the Syrian civil war.
The Syrian government used DarkComet to surveil and intimidate activists, leading to arrests, torture, and possibly deaths. The RAT's ability to access webcams and microphones led to severe invasions of privacy.
Blackshades RAT
Blackshades was a widely distributed RAT sold for as little as $40, making it accessible to a wide range of cyber criminals. In 2014, an international law enforcement operation led to the arrest of nearly 100 individuals involved in distributing and using Blackshades.
Tens of thousands of victims' systems, including personal computers, corporate networks, and government systems, were compromised. Victims faced financial losses from data theft, extortion, and fraud. The RAT was used to spy on individuals through their webcams, leading to numerous cases of blackmail and harassment.
Emotet and TrickBot
Emotet and TrickBot are malware families that have used RAT components to facilitate their operations. Their campaigns have targeted individuals, large corporations, and government agencies.
Organizations suffered financial losses from data breaches, ransom payments, and more. Hospitals and healthcare providers were particularly affected, with some attacks leading to the shutdown of critical healthcare services.
Current RATs in The Wild
Here are some RATs currently being used in the wild as of the writing of this article.
- Asyncrat is a Trojan that targets Windows systems. This malware sends information about the targeted system to a remote server, which commands it to download and execute plugins, kill processes, uninstall/update itself, and capture screenshots of the infected machine.
- NanoCore is a powerful RAT that targets Windows operating systems. It’s known for its wide range of features, including keylogging, remote desktop access, password theft, and the ability to control connected devices such as webcams and microphones.
- njRAT is a popular RAT frequently used by cyber criminals via phishing attacks and drive-by downloads for spying, data theft, and system manipulation. It’s often distributed via malicious email attachments and drive-by downloads. njRAT captures keystrokes, accesses the victim’s camera, steals credentials stored in browsers, and uploads and downloads files.
- Remcos (Remote Control and Surveillance Software) is a commercially available RAT that distributes itself through malicious software such as Microsoft Office documents attached to spam emails. It offers functionalities like keylogging remote desktop access and has been used in various phishing campaigns.
Detecting RATs
Detecting remote access trojans involves behavioral analysis, network monitoring, and specialized tools. Here’s a detailed overview of how RATs can be detected, common indicators of their presence, and best practices for monitoring.
Detection Methods
Certain signs may inform you of a RAT's presence. Look for unusual system behavior, such as unexpected network traffic, unusual file changes, or unrecognized processes running. Significant slowdowns or unresponsiveness can also indicate the presence of a RAT.
Monitor network traffic for unusual outbound connections, especially to unfamiliar IP addresses or domains. Identify and investigate unknown or suspicious processes running on the system and use tools to check for unexpected changes to critical system files.
Common Indicators of RAT Infection
Look out for the following signs that may indicate the presence of a remote access trojan.
- High outbound traffic volumes, especially to unknown external servers
- Strange error messages or unexpected windows appearing
- Sudden changes in system performance, like slowdowns, unexpected reboots, or applications opening/closing independently
- Unexplained user behavior like new user accounts or changes to security settings
- New files appearing or existing files being modified or deleted without user action
- Alerts from antivirus or endpoint protection tools indicating suspicious activity
Tools for Detection
Here are some common tools that can detect or help detect the presence of a remote access trojan.
Antivirus and Anti-malware Software
Examples: Bitdefender, Malwarebytes
Function: Detect and remove known RAT signatures and suspicious behavior patterns
Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS)
Examples: Snort, Suricata
Function: Monitor network traffic for signs of malicious activity and potentially block it
Network Traffic Analyzers
Examples: Wireshark, Zeek (formerly Bro)
Function: Capture and analyze network traffic to detect anomalies and suspicious connections
Endpoint Detection and Response (EDR) Tools
Examples: CrowdStrike Falcon, Carbon Black, SentinelOne
Function: Provide continuous monitoring and response capabilities for endpoint devices
File Integrity Monitoring Tools
Examples: Tripwire, OSSEC
Function: Monitor and alert on changes to critical system files
Best Practices for Monitoring and Prevention
We recommend following these best practices to monitor for and prevent RAT infections effectively.
- Ensure all systems and software are updated with the latest security patches.
- Train employees to recognize phishing attempts and avoid downloading suspicious files.
- Deploy multi-factor authentication to secure access to systems.
- Restrict user permissions to only what is necessary for their role.
- Conduct periodic security audits and vulnerability assessments.
- Segment networks to limit the spread of malware.
- Maintain regular backups.
- Have a recovery plan in place in case of an infection.
Additional Resources
The following resources may be helpful if you want more in-depth information on detecting and preventing RATs.
NIST Special Publication 800-83: This National Institute of Standards and Technology (NIST) publication guides preventing and handling malware incidents, including those involving remote access trojans.
MITRE ATT&CK Framework: The ATT&CK (Adversarial Tactics, Techniques, and Common Knowledge) framework developed by MITRE provides a comprehensive list of adversaries' techniques, including those related to RAT deployment and operation.
Implementing these detection methods, using appropriate tools, and following best practices can significantly enhance your ability to detect and respond to RAT infections.
Using RATs in Ethical Hacking and Red Team Engagements
We’ve seen how threat actors use RATs to cause harm. However, Ethical hackers or Red teamers can also use them to test a system's security and identify vulnerabilities before malicious actors do. Using RATs in a controlled environment can help identify weaknesses and recommend improvements to enhance security measures.
Let’s show you how this might be accomplished. We’ll discuss the technical execution and then give you an example scenario.
Technical execution:
You’ll need to either select a RAT already used in the wild or build and configure it independently. Next, you’ll need to set up a C2 server and then find a way to gain access to the system to deploy the RAT. Finally, you’ll need to extract as much data as you can.
1. Selecting a Pre-Existing RAT
Choose RATs commonly used by threat actors to simulate real-world attacks. Ensure the RAT has the necessary capabilities, such as remote control, keylogging, and data exfiltration. Opt for RATs, known for their ability to evade detection. You could choose something like NanoCore, njRAT, or DarkComet.
2. Building and Configuring Your RAT
If you need to develop your RAT, choose a language such as Python, C++, or Java. Determine which features you want it to have, such as keylogging or remote desktop control, and implement methods to obfuscate the code to evade detection.
Configure the RAT to communicate with your C2 server, ensuring encrypted communication. Add features that allow the RAT to maintain persistence on the target system, such as registry modifications or scheduled tasks.
3. Establishing a Command and Control (C2) Server
Use a VPS or cloud service to host your C2 server. Ensure communications between the RAT and the C2 server are encrypted using SSL/TLS. Use C2 frameworks like Cobalt Strike, Metasploit, or custom-built servers.
4. Gaining Access and Persistence
Use social engineering techniques such as phishing emails with malicious attachments or links. Once the target interacts with the payload, the RAT is installed and initiates a connection to the C2 server.
Implement mechanisms like modifying startup scripts, creating scheduled tasks, or using rootkits to maintain persistence. Ensure the RAT operates covertly to avoid detection by security tools and system administrators.
5. Extracting Data
Use the RAT to log keystrokes, capture screenshots, and access sensitive files. Securely send collected data back to the C2 server using encrypted channels.
Example scenario
Let’s walk through a theoretical red team engagement scenario using the RAT we created in the previous step.
Step 1. Initial Access:
- A spear-phishing email is sent with a malicious attachment.
- The target opens the attachment, which exploits a vulnerability to install the RAT.
Step 2. Establishing Connection
- The RAT connects to a pre-configured C2 server hosted on a secure VPS.
- The connection is encrypted using SSL/TLS.
Step 3. Persistence
- The RAT modifies registry keys to ensure it runs at startup.
Step 4. Data Collection
- The RAT logs keystrokes and captures screenshots of sensitive applications.
Step 5. Data Exfiltration
- Collected data is returned to the C2 server over an encrypted HTTPS connection.
Step 6. Reporting
- The red team analyzes the data and techniques for gaining and maintaining access.
- The organization receives a report detailing the attack vectors, persistence mechanisms, and recommendations for improving security defenses.
Conclusion
You should now clearly understand what a remote access trojan is, including its threats and effective defense strategies.
Remote access trojans are incredibly dangerous types of malware that can cause significant damage to both individuals and organizations.
In this article, you've seen real-world examples of how they can steal sensitive data and take control of systems, and we’ve shown you how they can be used to protect organizations by allowing red teams to test their security defenses.
If you want to learn more about the effects of malware in cyber security or how to become a penetration tester, join the StationX Accelerator Program today and begin your journey to becoming a skilled professional with our courses, mentorships, roadmaps, and more.
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