How to Know If Someone Was Secretly Using Your Computer
Now that we’re all sharing our home workspace with roommates, friends, and loved ones, it’s worth thinking a little more about the security of your laptop or desktop computer. When someone uses your computer without your permission, it can seem like a small invasion of privacy, especially if you suspect that they are doing it with malicious intent.
If you believe that a nosy roommate, brother, sister, or partner is accessing your computer without your permission – for whatever reason – here’s how you can find out and regain some privacy.
How to know if someone else has access to your computer
Before you fight the person who you think was using your computer, you should take a few minutes to gather some information. If someone has tinkered with your machine, it may be helpful to know more about what they did. This includes checking logged events, recently opened applications and documents, and browser history.
Check the logged events on your PC
You can use the Windows Event Viewer to get an idea of any activity that happened while you were away from your computer. To get started, click the Start button and start typing Event, then select Event Viewer when it appears. Once you’re there:
- Toggle open Windows logs in the left pane.
- Left-click on “System” and then find the “Filter Current Log” option in the right sidebar. This allows you to isolate specific events, event types and times.
- From the Registered drop-down list, select Custom Range … and then Events Enabled from the drop-down menu to narrow the search box to the point where you think your computer was accessed. Select OK.
- From here, you can click OK to just view all the events, or you can filter them by specific event IDs or task categories.
Generally speaking, you won’t understand what most of these events mean, and that’s okay. More importantly, is there a ton of events happening at a time when you knew your computer was turned off. If so, it may have been used – something you can also check by clicking Applications and Services Logs in the left sidebar and then Microsoft> Windows> Diagnostics-Performance> Operations. From there, search for event IDs 100 and 200 to find out when your system turns on or off.
Check logged events on your Mac
Mac users have a little handy way of knowing when their displays are turning on and off, giving you an idea of whether someone else has used your system while you were away. (Unless, of course, your dog or cat hit your Magic Mouse. We can’t help you with that.)
To start:
- Open Finder and click the “Go” menu and then select “Go to Folder …”
- Enter
/var/logand click Go. - Find and double-click the “powermanagement” folder.
- From here, you will see a bunch of .ASL files named after specific dates. Open one for the date you’re interested in.
- In the console that appears, click on the search bar, type
displayand press Enter.
You will now see a list of times your display has turned on and off. If you were away from home or knew that your Mac was (presumably) turned off at the time, this could be a sign that someone was trying to access your system. It’s also a great reminder to always lock your Mac with a strong password .
Check your documents and attachments for recent activity
If you’re on PC …
Open File Explorer and find the “Quick Access” section, which should display the most recent files open on your system. You can also navigate through the document and load folders to see if any files were changed at an odd time, or just run a simple *.* Search in a folder and thus check the file modification time. In addition, most applications provide a list of recently opened files. Open a few common ones (Word, Excel, VLC, Photoshop, etc.) to see if anyone has spied on.
If you don’t want to waste time digging through the program menus, you can use free utilities such as ExecutedProgramsList and LastActivityView, which compile and display information about when files and applications were last opened, as well as other actions performed on your computer (for example, logging in). and folder views).
For Mac Users …
Click the Apple icon in the upper-left corner of the menu bar and hover over Recent Items. This will show you the 10 most recently open applications, documents and servers.
Then open Finder, click Go in the menu bar, and hover your mouse over Recent Folders to view recently used folders and drives. You can also open a Finder window and re-click the Name / Date Modified / Size / Type columns to add the “last opened” date and time — a convenient way to see if someone has tried to view your files while you’re away.
Check your browser history
Most web browsers make it fairly easy to view your browsing history (assuming someone accessing your system hasn’t cleared it, which might be a clue). For example, in Chrome, click the three dots icon in the upper right corner and select History. You will see recently visited and recently closed pages, or you can click the History link to see everything.
The steps are similar in Firefox and Safari – and in most browsers, pressing CTRL + H should be all you need to do to open history (or Command + Y on a Mac, or Command + Shift + H, and so on).
Now that you have a good idea of how to determine if someone is sniffing your computer, let’s take a look at a few steps you can take to block it.
Update your password (and, you know, use it )
Your computer password is your first line of defense against intruders. If your computer is not password protected, set it up now with our guide to help you create a secure password .
If you already use a password for your computer, but have widely shared it with the people you live with, or if you haven’t updated your login credentials with something easy to guess, change it to something better. Heck, if you have the slightest suspicion that someone might gain access to your computer when you are not at home, change your password . Use something unique that you don’t use anywhere else, and of course, something that is not so easy to guess by those with whom you live.
Remember to lock your screen
Make sure you lock the screen every time you leave your computer. When you do, you (or the observer) will have to re-enter your password in order to log back in – an easy way to keep people out of your system who don’t know your credentials.
On a PC, the fastest way to lock the screen is to press the Windows + L keys on your keyboard. On a Mac, the keyboard shortcut is Control + Command + Q. (As an extra precaution, make sure your Mac is set to prompt for a password immediately after it goes to sleep. You will find this option in System Preferences> Security & Privacy .) You can also customize how long your Mac will be idle before going to sleep in System Preferences> Power Saver .
Install anti-theft apps or cameras
If you want to catch a spy in the act, you probably need a third-party app to really understand what’s going on.
We love the Do Not Disturb mode for Mac , which notifies you whenever someone interferes with your hardware. You can also use anti-theft software like Prey , which comes with many features to track and lock your car if it is found or stolen.
Finally, consider installing video surveillance (hidden with a good view of your car) to track your activities. Use a cheap security camera with motion alerts,make your own camera with a Raspberry Pi, or turn your device’s webcam into a security camera using an app like iSpy .
Of course, protecting your computer and your data from digital spyware is a completely different topic. Use these tips to protect your hardware, then make sure you are properly protecting yourself with antivirus and malware protection .
This article was originally published in 2012 by Whitson Gordon and updated in April 2020 by Emily Long and David Murphy. We’ve reworked the article significantly, adding additional tips and links to new third-party apps, rewriting parts of the article to clarify new instructions, and changed (or inserted) screenshots. We left Whitson’s signature on the article as an indication of his original work, thoughts, and ideas.