Shared computer showing up in Finder

A device listed in the Finder Sidebar as "Shared" is on your network, certainly, but it is OFFERING to be connected TO, rather than necessarily connecting to YOU and reading your files. Obviously, if you have an unprotected Public folder, then those could be read.

If you really think it is an intruder, then access your router's setup and see if the MAC address of that device is listed. If it is, that may even tell you something about the type of hardware; and you can then blacklist it (or whitelist only your equipment).

As you will see in other similar threads, these devices are usually the router itself, or a wireless printer. However, the name does perhaps indicate someone's laptop.

Why not tell us the complete name of the device? That might be useful, and if it is an intruder, you don't owe him any protection -- and there's not much that knowing the name will achieve in terms of being able to compromise him.

 

You didn't mention what type of security you chose. If you chose WEP, then that is your problem - WEP is very easy to break. If this is the case, reconfigure your router using WPA.

Also, some routers have a "guest" feature. With this guest feature, it basically acts as if you have 2 access points - one protected and one unprotected. If your router has this feature, make sure you are connecting to the protected connection. You might even want to turn off guess access since you know you have a neighbor stealing your bandwidth without your permission.

You might also look to see if your router has a way to blacklist MAC addresses.

Also, since you know his name is davenel***, you should go find him and give him a swift kick in the nuts.