|Don't use wireless. The problem with wireless is that you send every thing out into the air which can be intercepted and decrypted. |
If you want to prevent the hacker from gaining access to your systems through the wireless you can use MAC filtering in addition. This will allow computers with specific MAC addresses to connect to your router only. You can get your computer MACs by doing an IPCONFIG /ALL.
All of this can be broken by known techniques that I can't mention that are available on the Internet.
Now getting down to the problem at hand. Catching a hacker is much like trying to catch a thief. Most hacks are done by someone you know and usually through physical contact with your computer. They install something called a Trojan which establishes a connection to their server on the Internet. Most firewalls are One Way which means they block attacks from the out side not from within. What the hacker will do is install a Keylogger on your computer which logs your key strokes and the Trojan will phone home with its logs.
The other way a Hacker can get a Trojan on your computer is through you. They either send you an email with an attachment or you download it through a Bit-torrent. I have seen trojans come from Key Generators that come with illegal copies of software like MS-Office that you down load from a bit-torrent like Lime Wire. When you run the app to generate a key that you can use to install Office it asks you to install the key generator which installs the Trojan. I can't tell you how many times I have cleaned up a computer that has been infested this way.
The best way to find this is by using NETSTAT /B which will tell which application/services have active connections to the internet and the address they are connecting to. Then you can use one of the WHO IS lookups on the internet to check each of the connections to know who they are. If it is Google then it is probably safe but if it it is a major ISP like Comcast then chances are it is the hacker unless you are with Comcast and you get your email or other services with them. You have to have a good under standing of the well known ports and what to look for to use this tool. Most often anti-viruses will do this for you but if you get a really good hacker then you will need to work at this level.
Personally, I don't do banking over WiFi. Have two computers or a docking station were you can hook into a hard line to do this. I prefer two computers because I use one for fun and one for business. This way if my fun computer gets corrupted it does not affect my business computer.