How to Find a Trojan on a Computer?

Yes, you can find a trojan on a computer by spotting clues and running targeted scans with trusted tools.

Worried that something nasty slipped onto your PC or Mac? This guide lays out clear checks and safe scans that catch hidden threats without panic moves. You’ll start with fast signals that point to trouble, then move through step-by-step methods that root out a stubborn trojan while keeping your files safe.

Quick Signals That Point To A Trojan

Begin with low-risk checks. These hints don’t prove a compromise, but they help you decide how deep to dig and which scan to run next.

Signal	Where To Check	What It Often Means
Fan ramps hard while idle	Task Manager / Activity Monitor	Hidden process eating CPU or GPU
Unknown startup items	Windows Startup apps; macOS Login Items	Persistence planted by a loader
Browser home page or search changed	Browser settings and extensions	Hijacker or add-on dropped by a bundle
Strange outbound traffic	Resource Monitor / Activity Monitor > Network	Beaconing to a command server
Files locked or renamed	Recent files; Documents	Payload tried to tamper or ransom
Security tool disabled	Windows Security or third-party AV	Malware interference
Unexpected prompts for admin rights	During installs or updates	Dropper seeking elevation
Frequent crash loops	Event Viewer / Console logs	Driver hook or bad kernel extension

How To Find A Trojan On A Computer: Step-By-Step

1) Prep: Isolate And Safeguard

Unplug risky connections. Pause file-sync apps. Copy irreplaceable documents and photos to a clean USB drive or cloud folder so a heavy scan doesn’t put them at risk. Skip copying installers, archives, or anything you downloaded near the time symptoms started.

2) Snapshot What’s Running

On Windows, press Ctrl+Shift+Esc for Task Manager. Sort by CPU, then Memory, then Disk. On macOS, open Spotlight and search for Activity Monitor. Look for odd names, unsigned publishers, or apps chewing resources when no big task is underway. Right-click a process and open its file location to see where it lives. A legit app tucked into a Temp folder is a red flag.

3) Check Startup And Scheduled Tasks

On Windows, open Settings > Apps > Startup and also run taskschd.msc to review scheduled tasks. Remove entries you never installed. On macOS, open System Settings > General > Login Items and review both “Open at Login” and “Allow in the background.” Remove unknown items, then restart and confirm they don’t reappear.

4) Run A Smart Scan, Then A Full Scan

In Windows Security, open Virus & threat protection. Run a Quick scan to catch active items fast. Follow up with a Full scan for a deep sweep. If alerts appear, follow the prompts, quarantine or remove, and restart if asked. Rerun the Full scan after the restart to confirm a clean state.

5) Add A Second Opinion

Use a reputable on-demand scanner to double-check loaders and droppers. A second engine often spots a pattern your main AV missed. Pick tools that can run without a full install, so the trojan has less room to interfere.

6) Scan Offline If The Threat Fights Back

If detections keep returning, scan before the OS starts. Windows offers an offline scan that reboots into a trusted mini-environment and scans the disk while the payload sleeps. Rescue media from a trusted vendor works the same way. This step removes pests that block or kill scanners during normal boot.

7) Clear Browser Add-ons And Reset Settings

Open each browser you use. Remove extensions you don’t trust or don’t remember installing. Reset the default search and home page. Clear any scheduled tasks or policies a hijacker created. Then sign out of the browser and sign back in to sync clean settings across devices.

8) Review Network Activity

Open Resource Monitor on Windows or the Network tab in Activity Monitor on macOS. Sort by “Sent” and “Received.” Unknown apps that chat with remote hosts while idle deserve a closer look. Block them with your firewall and run another scan. If you run a desktop firewall, add rules that alert when a new program asks for outbound access.

Windows: Exact Places To Look

Task Manager Views That Help

In Processes, sort by CPU and Disk to spot spikes. In App history, look for odd surges over the last few hours. In the Startup tab, disable entries you don’t recognize and reboot to test. Use “Open file location” on a suspect process and check its folder. Signed binaries stored in a random AppData\\Local\\Temp path aren’t normal.

File Locations That Often Hold Trouble

%ProgramData%\\ and %AppData%\\ subfolders with random names
C:\\Users\\<name>\\AppData\\Local\\Temp\\ with recent EXE or DLL drops
C:\\Windows\\Tasks and the Task Scheduler Library with odd triggers and paths

Built-In Scans Worth Running

Use Quick, Full, and Offline scans in Windows Security. You can also run the Microsoft Malicious Software Removal Tool to clean widespread families that linger on older systems. It updates monthly and targets active infections. Keep everything patched through Windows Update so the engine and definitions stay current.

macOS: Exact Places To Look

Activity Monitor Checks

Sort by CPU, Memory, and Energy. If a process name looks strange, use “Open Files and Ports” to view its path. Quit only if you know what it is, then follow with a scan. If the same item relaunches, search for a matching Login Item or LaunchAgent.

Login Items, Profiles, And Launch Agents

Open System Settings > General > Login Items. Remove unknown entries under both sections. Then open System Settings > Privacy & Security and check for profiles you didn’t install. Look in ~/Library/LaunchAgents and /Library/LaunchAgents for odd .plist files with recent timestamps. Move suspicious items to a quarantine folder on your desktop and restart.

Browser And DNS Cleanup

Reset Safari, Chrome, and Firefox settings. Remove search providers you don’t recognize. In Network settings, confirm DNS points to your router or a known resolver. If it points to an unknown address, change it, then scan again.

When The Scan Finds Something

Quarantine or remove the detected item using your scanner’s prompt. Restart if asked. Run a Full scan again to confirm. If the scanner lists “not remediated,” use an offline scan or a rescue USB from a trusted vendor and try again. If business data or regulated data is at stake, escalate to an incident response pro and preserve logs.

How To Confirm A Clean State

Run two different engines back-to-back. Fresh definitions on both.
Reboot twice and confirm that startup items stay clean.
Open Resource Monitor or Activity Monitor and watch for quiet network use while idle.
Patch the OS and browsers. Old builds invite repeat trouble.
Rotate passwords on accounts used since the infection window. Turn on two-step sign-in.

Close Variation: Finding A Trojan On Your Computer Safely

This section sums up habits that cut risk and raise your odds of spotting a fake installer next time.

Safer Install Habits

Download only from the vendor site or a known store.
Skip “cracked” bundles and random driver packs.
During setup, pick Custom and untick add-ons you don’t need.
Scan archives before extracting. Avoid double-extension files like .pdf.exe.

Email And Messaging Hygiene

Don’t run attachments you didn’t ask for, even if the sender name looks familiar.
Hover on links. If the domain looks off, don’t click.
Use webmail’s built-in preview for unknown documents instead of downloading.

Account And Password Hygiene

Turn on two-step sign-in where you can.
Use a password manager and unique passwords.
If your scan found a stealer, change passwords from a clean device.

Network Hygiene

Keep router firmware current.
Use WPA2 or WPA3 with a strong passphrase.
Disable remote admin on home routers unless you need it.
If you run a desktop firewall, enable alerts for new outbound connections.

Scan Types And When To Use Them

Scan Type	Use It When	How To Start
Quick scan	You want a fast check of hot spots	Windows Security or your AV app
Full scan	You saw strong signs or recent alerts	Windows Security or AV settings
Offline scan	Threat returns after cleanups	Windows Security > Scan options
On-demand second opinion	Main AV found nothing	Download a reputable scanner
Bootable rescue media	System won’t start or AV is blocked	Create vendor USB and boot it
macOS malware scan	Login Items show unknown entries	Use a trusted Mac scanner
Cloud file check	You need to test a single file	Upload to a multi-engine service

Policy-Backed Help And When To Escalate

If a workstation handles sensitive data, treat any confirmed trojan as a security incident. Segment the device from the network, save logs for your admin, and follow your company’s response plan. For home users, keep copies of scan reports and note the time you saw alerts. If you can’t clear it after an offline scan, a fresh install saves time.

Trusted References For Further Reading

Security teams publish step-by-step advice on spotting, scanning, and cleaning malware. See the broad guidance from CISA on malware and Microsoft’s monthly Malicious Software Removal Tool page for what it targets and how updates roll out.

Exact Phrase In Context

If someone asks “how to find a trojan on a computer,” point them to the quick signals table, then the step list. The mix of visual checks and staged scans usually catches both loaders and their payloads. If a small office asks “how to find a trojan on a computer,” add offline scans and a router check to the plan, then rotate passwords from a clean device.