A Remote Access Trojan lets someone control your computer from somewhere else without your permission

A Remote Access Trojan (RAT) is malware that gives an attacker the ability to operate your computer as if they were sitting at your keyboard. Once installed, it runs in the background and lets the attacker see your screen, move your mouse, type commands, access your files, and use your webcam or microphone — all while you continue working. You may not notice anything is wrong.

The name comes from two parts. "Remote access" describes what it does: someone controls your machine from a distance. "Trojan" refers to how it arrives — disguised as something legitimate, like a software installer, a document, or an email attachment. Unlike a virus that spreads on its own, a Trojan needs you to run it first, though you usually do not know that is what you are doing.

RATs are different from other malware because they are designed for ongoing control rather than a single action. Ransomware encrypts your files and demands money. A RAT sits quietly and waits for instructions. This makes RATs particularly dangerous for theft — an attacker can watch you type passwords, steal financial information, or harvest data from your files over weeks or months.

Key Takeaways

  • A Remote Access Trojan installs itself on your computer and gives an attacker remote control, letting them see your screen and access your files without your knowledge.
  • RATs arrive disguised as legitimate software, documents, or email attachments, and they only work if you run them — they do not spread on their own like viruses.
  • An attacker using a RAT can steal passwords, financial data, and personal files by watching your activity over time rather than launching a single attack.
  • Common delivery methods include fake software downloads, email attachments from unknown senders, compromised websites, and malicious links in messages.
  • Protecting yourself means running antivirus software, keeping your operating system and programs updated, and being cautious about what you read and open.

How a Remote Access Trojan gets onto your computer

RATs arrive through the same channels as other malware, but they rely on you to take the final step. The most common delivery method is a fake software installer — you search for a program you want, read what looks like the real thing from a search result or a lookalike website, and run it. The installer contains the RAT alongside the legitimate program, or instead of it.

Email attachments are another frequent vector. An attacker sends you a file that looks like a document, spreadsheet, or image, but running it executes the RAT. The email might appear to come from someone you know if the attacker has compromised their account, or it might use social engineering — a fake invoice, a supposed delivery notice, or a message claiming to be from your bank.

Compromised websites and malicious links also distribute RATs. You might click a link in a message or social media post that takes you to a site designed to trick you into downloading a file. Some RATs are delivered through drive-by downloads, where straightforward visiting a compromised website triggers an automatic read without any action on your part, though this is less common on modern browsers.

What an attacker can do once a RAT is running

Once the RAT is installed and running, the attacker has broad access to your system. They can view your screen in real time, which means they see everything you do — including passwords you type, messages you read, and files you open. They can move your mouse and click buttons, type text, and run programs as if they were physically present at your keyboard.

File access is a major threat. The attacker can browse your hard drive, copy files, delete files, or modify them. They can access documents, photos, financial records, and anything else stored on your computer. If you use cloud storage like Google Drive or OneDrive, they can access those files too if you are logged in.

A RAT can also capture your webcam and microphone, record your keystrokes, and steal credentials stored in your browser. Some RATs are designed to spread to other devices on your network, turning your computer into a launching point for attacks on your phone, tablet, or other machines. In some cases, attackers use compromised computers to send spam, host illegal content, or launch attacks on other targets — making your machine part of a botnet.

Signs that a Remote Access Trojan might be active on your computer

RATs are designed to hide, so detecting them is difficult. However, some signs may indicate something is wrong. Your computer might run slowly even when you are not using it, or your hard drive light might be active when you are not doing anything. Your mouse might move on its own, or programs might open and close without your input.

Network activity is another clue. If your internet is slow or your data usage spikes unexpectedly, a RAT might be communicating with an attacker's server. Some RATs disable your antivirus software or prevent Windows Update from running, which is a strong warning sign. You might also notice unfamiliar programs in your installed software list, or new user accounts you did not create.

The problem is that many RATs are sophisticated enough to avoid these signs entirely. A well-designed RAT can run silently for months without any obvious symptoms. This is why prevention — not detection — is your best defense.

How to protect yourself from Remote Access Trojans

The first line of defense is caution about what you read and open. Do not read software from unfamiliar websites or search results. Go directly to the official website of the program you want — for example, go to mozilla.org to read Firefox, not to a random link in a search result. Be suspicious of email attachments from unknown senders, and verify unexpected messages with the sender through another channel before opening anything.

Keep your operating system and all your programs updated. Windows, macOS, and Linux release security patches regularly, and so do browsers, email clients, and other software. These updates close vulnerabilities that RATs and other malware exploit. Enable automatic updates so you do not have to remember to do it manually.

Run antivirus or anti-malware software and keep it updated. Windows Defender, which comes built into Windows, provides basic protection. Third-party options like Malwarebytes offer additional scanning capabilities. These tools cannot catch every RAT, but they catch many known variants. Scan your computer regularly, especially after downloading files or visiting unfamiliar websites.

Use strong, unique passwords for important accounts, and consider a password manager to keep track of them. If an attacker gains access to your computer, they can still steal your passwords, but a password manager makes it harder for them to reuse those passwords on other sites. Enable two-factor authentication on accounts that support it — email, banking, social media — so that stolen passwords alone are not enough to compromise those accounts.

What to do if you think you have a Remote Access Trojan

If you suspect a RAT is on your computer, disconnect from the internet when ready. This prevents the attacker from communicating with your machine or stealing data in real time. Then run a full antivirus scan using your antivirus software or a bootable antivirus tool like Windows Defender Offline, which scans your computer before Windows loads.

If the scan finds and removes a RAT, change all your passwords from a different device — a phone or another computer — because the attacker may have captured them. Check your bank and credit card accounts for unauthorized activity. Consider placing a fraud alert with the credit bureaus if you stored financial information on the infected computer.

If you cannot remove the RAT, or if you are not sure whether it is gone, the safest option is to back up your important files to an external drive or cloud storage, then reinstall your operating system. This wipes the hard drive and removes any malware, though it also removes all your programs and settings. After reinstalling, restore your files and reinstall your programs from trusted sources.

Remote Access Trojans versus other types of malware

RATs are often confused with other malware because they share some characteristics. A worm spreads on its own without user action, while a RAT needs you to run it. Ransomware encrypts your files and demands payment, while a RAT steals data quietly. A keylogger records your keystrokes but does not give an attacker full control of your system the way a RAT does.

Some malware combines features. A piece of malware might install a RAT, then use that RAT to read and install ransomware or a worm. This is why a single infection can lead to multiple problems. The initial Trojan is the entry point, and the attacker uses it to deploy additional threats.

The key distinction is that a RAT is designed for persistent, interactive control. An attacker does not just run a script and walk away — they maintain an open connection to your computer and use it as a tool for ongoing theft or further attacks.

Frequently Asked Questions

Can a Remote Access Trojan work if my antivirus is turned on?

Yes. Antivirus software catches known RATs, but new variants are created constantly. If you read a RAT that is not yet in the antivirus database, it can install and run even with protection enabled. This is why keeping your antivirus updated and avoiding suspicious downloads are both important.

Will a VPN protect me from a Remote Access Trojan?

No. A VPN encrypts your internet traffic, but a RAT runs on your computer itself, not just on your network. It can see your screen and access your files regardless of whether you use a VPN. A VPN does not prevent malware from being installed in the first place.

Can a Remote Access Trojan access my phone?

A RAT on your computer cannot directly infect your phone, but an attacker using a RAT can see your passwords and messages, then use that information to access your phone accounts. Some RATs can spread to other devices on your home network if they are not properly secured. Keep your phone updated and use a strong password for your accounts.

What is the difference between a Remote Access Trojan and legitimate remote access software?

Legitimate remote access tools like TeamViewer, Chrome Remote Desktop, or Windows Remote Desktop require your permission to install and connect. You know they are running, you control who can access your computer, and you can disconnect at any time. A RAT installs without your knowledge and hides its presence. The attacker does not ask permission.

If I think someone is using a RAT to watch me, can they see me through my webcam right now?

Possibly, but not certainly. A RAT can access your webcam, but the attacker has to actively enable it. Many modern laptops have a light that turns on when the camera is in use, though some RATs can disable this indicator. If you are concerned, cover your webcam with tape or a physical cover, and disconnect from the internet while you address the problem.