How to check if I am being attacked or have already been attacked??

Hi I am new to here and found it on Google. Sorry to skip some introduction and let me ask my questions straightforward.

A few hours ago I had trouble with someone on the internet in which he claimed to attack / hack my PC because he had my IP address. He does really have my IP address because I visited his website with Chrome or Firefox browsers. His website also showed my IP address.

I didn't provide any other personal information to him consciously. All he might have is my IP address and the record of me browsing his site. I am connecting to the internet with my desktop PC (not WIFI but I've got a wireless router), I am using Windows 7 Home Premium. I didn't install any Firewall software but Control Panel suggests that I am ''connected'' to the Firewall which is a little bit confusing to me.


Questions are
1. According to my computer setting (Windows 7 home premium, no firewall, no Anti-virus, my internet is connected as soon as the cable is plugged, no username or password is required), how likely I am already hacked or attacked?

2. I have just released and renewed my IP at router's setting. However, it has been a few hours already from now. Can I check (and how to??) if my PC is already attacked / hacked or being attacked hacked now??

3. Is it possible he could not copy or delete any of my files but he could watch my activity on his screen like what I am seeing on my screen now??

Note: He is NOT Police or gov sector whom might have special ability and permission to do that and I am not a criminal. He is just an individual, but chances are he is a tech geek or even a hacker. I am just an average user (whom with some important data on my computer) , and he has my IP. I am quite worried about if I am being hacked now or already been hacked.

Thank you for all comments in advance.

ignatzatsonic said:

Did he want money to not attack you?

What was his motivation to attack you?

He could be a scammer who was trying to get money out of you, sooner or later.

Your IP address at any moment is not hard to get.

Why aren't you using anti-virus and anti-malware applications?

What is the URL of his website?

He did not ask for money not to attack me

His motivation is because we had bad conflicts. He could just hate me.

However, I don't want to guess anything. I just wish to know how to check if my computer is already or being attacked/ accessed by unauthorized traffic.

Thanks

yanyan said:

1. According to my computer setting (Windows 7 home premium, no firewall, no Anti-virus, my internet is connected as soon as the cable is plugged, no username or password is required), how likely I am already hacked or attacked?

VERY unlikely. Reading the post, it sounds to me that it's just some bully claiming he can hack into your computer, but he really has no idea how to actually do it, some people do so just to appear to be important but without knowing what they're talking about.
Most home computers really sit behind some form of NAT, be it from the router/modem or done by the ISP, and with that, the IP address become irrelevant. But if you happen to host some kind of server or port forwarding it might become an attack vector should a vulnerability in them appears. Additionally, the IP itself is easily obtainable by many means, and that's not a problem (it's called public IP for a reason).

If he really wants to attack you, the most convenient way to do is to introduce an attack in his website, possibly exploiting a vulnerability in Flash/Java/Internet Explorer. That would not be directed at you however, but to all visitors. It's also relatively easy to mitigate those by updating the software and running the browser under more limited permissions.

In short, while we can't dismiss the chance of an attack, I find it very unlikely to actually occur one.

yanyan said:

2. I have just released and renewed my IP at router's setting. However, it has been a few hours already from now. Can I check (and how to??) if my PC is already attacked / hacked or being attacked hacked now??

Checking the process list for anything strange would be a first step, specifically looking for any program that you don't know. Antiviruses might be of some use too. To be extra sure, system restore could remove any thing he could have done. Cleaning browsers cache can also help.

yanyan said:

3. Is it possible he could not copy or delete any of my files but he could watch my activity on his screen like what I am seeing on my screen now??

Teoretically possible, yes. In practice it's extermely difficult. He would need to run some program in your computer to do anything like that. That's usually done exploiting some bug in the browser or addin, or most likely with an infected download that you run. With careful browsing, patched software and proper security practices chances of that really happening are minimal.

You might like the free tool mentioned in this post.