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There are ways how to tell if someone has been on your computer and to keep prying eyes away from your computer in your home. You can secure it with a USB drive, Windows logon password, or even a BIOS password. You can also lock programs and even word documents. However, as with most security attempts, there's usually a way around them. Security is basically a deterrent and the more work you make for a snoop, the less likely you are to become a victim.
I list the key points below on how to monitor your system and check for the signs of spy software:
AntiSpy Programs: AntiSpy programs look for signatures or traces that are specific to certain spy software. Some simply do text string scanning to find them, and others actually extract and attempt to remove the spyware.
System Resources: Poorly written spy software will usually put an enormous drag on system resources. Watch out for poor system resources, running out of memory, lots of hard disk activity or a screen that flickers. This is caused by some spy software programs as they take snapshots of the computer screen that requires system resources.
AntiVirus & Firewall: Many antivirus programs can catch prolific spy software because they are often classified as Trojan Horses. Keep spy software up to date and make sure it is running in the background. Firewalls will also alert you to both inbound and outbound activity. You can control programs allowed in and out of your system. Watch for suspicious programs you do not recognize trying to send data out of your system.
Be careful about what you install on your system. Don't run email attachments and read the EULA (end user license agreement). Keep an UpToDate AntiSpy Package on your machine.
If you suspect someone has obtained physical access to your computer with the intent to spy on you, you should take your computer and keyboard to someone who is a specialist in computer forensics and have it checked, there are hardware devices that can be affixed to your keyboard and inside your computer that can monitor your activities.
I'm just about to watch a movie, but I wanted to post a quick reply. This sounds like an entirely messed up situation. That is not normal behavior. You might want to consider speaking to an attorney and looking into a restraining order.
I would change the SSID and password on your router immediately. Sure, it's possible that he gained access. That doesn't mean he has but if, for instance, you are using WEP for router security it's pretty easy. Not so easy if you have a WPA2 router/modem. It's easy to change, so do it.
Is it possible that someone could view and listen to you through your webcame. A RAT (remote admin tool) will allow someone to control your computer remotely. Software such as FinFisher will allow for live surveilance through the microphone and webcam, but I don't think the general public can purchase FinFisher. I'm sure there is are other options though. Other things that have been used in the past include keyloggers that record every keystroke you make. It is unlikely that this type of software could have been installed by him unless he had physical access to your computer.
I am certainly not saying that any of this is happening. In fact, it probably isn't because it isn't particularly easy to do. But worst case scenario, it is a possibility. To be safe, change passwords on everything (online accounts, router, etc.). One thing I do out of pure paranoia is put a piece of tape over my laptop's webcame. Otherwise I feel like it is staring at me. Start using a password on your laptop and set it to hibernate at least when you close it. Run a malware scan on your computers (there are a number of free options, Malwarebytes is what I use). Enable a firewall on your computers (again there are a number of options, I'm a Windows users and use either the built in firewall or Comodo).
I hope everything turns out ok. One thing that is easy to do is start seeing EVERYTHING as suspicious, and walk around consumed with paranoia. Try to stay calm and approach this as rationally as possible and keep records of everything. Also, as I said before, you should seriously consider speaking with an attorney about this. Best of luck to you.