If someone hacks my wi-fi password, what can they see and how?
If someone knows my wifi password (be it WEP or WPA) what can they see? Do they just see URLs I visit, or can they see everything in my browser, or even everything I do on my computer? Does using HTTPS make any difference?
Secondly, If the attacker does not live nearby, is it possible for them to set up a laptop in my neighbour's house and record all my traffic or otherwise relay the data via the web?
Please provide more detail on your configuration, such as what operating system you're using, if you're sharing any local resources (files and directories, web cameras,...) through your private network, if you have some remote controlled desktop applications installed and enabled, do you use software firewall or use torrent clients and which, what anti-virus/anti-spyware software do you have installed, and similar information that might help the community in answering your question more completely. Don't be too specific, though. Naming them would be helpful enough. ;) Cheers!
windows 7,no remote control apps, no firewall or antivirus, use utorrent occasionally.
They would see the same thing that they would see if they snuck into your house and plugged their laptop into your ethernet hub with an ethernet cable. And could either sniff traffic or directly connect to any computer on your network allowing them to do anything they wanted.
If someone knows my wifi password (be it WEP or WPA) what can they see on my screen? Do they just see URLs I visit, or can they see everything in my browser,....or can they see everything I do on my computer? Does using HTTPS make any difference?
They can't see anything on your screen (unless you've enabled some sort of unencrypted remote desktop screen sharing program).
They can, however, observe all the data being sent to and from your computer (I'm assuming for WPA/WPA2 they observed the 4-way handshake at the beginning of each session; or trivially forced your computer to start another handshake), unless you encrypted that data using a protocol like HTTPS. They would typically run a packet capture program like wireshark to decrypt the wifi encryption.
Again, they'd be able to see what HTTP webpages you requested, what links you click, the HTML content of the webpages you requested, any information you post to a web site, as well as all data (e.g., any images/movies) sent to you or by you. They can also interfere with the traffic being sent to you (e.g., alter the content you see). Granted anyone nearby can always interfere and cause denial of wifi service without knowing your password (e.g., often turning on a microwave oven will interfere with all wifi traffic being sent to you). Or have their own computer/router that they fully control that sends impersonated messages as you or your router.
If you visit HTTPS sites only, they can't decrypt the data (unless they have somehow additionally compromised your computer). However, even with HTTPS they can see what IP addresses you are sending/getting data from (which usually will let them tell what domain e.g. if you went to 18.104.22.168 it's
stackexchange.com). They also will know when and how much encrypted data is being sent. This is possibly enough to give away private information. Imagine you went to a webpage via HTTPS that had results of your HIV test, and an eavesdropper was listening. If the web page for a negative result showed 3 images (of specific sizes) and a 10 MB PDF file on safe sex, while the page for positive results had 15 images and three PDF files that were 8MB, 15MB, and 25 MB respectively you may be able to figure out what their results were by observing how much data was sent and when. This style of attack has been used to figure out what people were searching for on a popular search engine (from the instant results provided for different queries) or roughly estimate what kind of income someone had at an https tax site. See Side-Channel Leaks in Web Applications (pdf).
Granted all this information is also available to your ISP as well and to every intermediary router between your computer and the server you are trying to visit.
Secondly, if the attacker does NOT live nearby, is it possible for them to set up a laptop in my neighbours house for example, and programatically record all my traffic...or alternatively can they relay the data from the laptop to their own computer elsewhere, via the web?
Either is trivial to program up assuming your neighbor doesn't mind them putting a laptop in their house (or they found a power source and place to hide their computer).
@user20378 - the attacker can write a simple script to capture your data and then forward it to some server they control.
Moral of the story is wireless traffic is easier to intercept than wired traffic. Unless your neighbour is an electrical engineer, spying on wired traffic is mostly the domain of governments.
@LateralFractal - Agree that wireless is easier to eavesdrop than wired. However, in addition to governments, includes anyone upstream of your network connection can eavesdrop/alter your traffic. Including for example your ISP, or network administrators at your work, etc can intercept unencrypted wired traffic.
@drjimbob, Regarding *"if you went to 22.214.171.124 its stackexchange.com"*, Does IPSec solve the ip-leaking problem? Are there even ways to solve this problem?