uBlock Origin is NOT an “ad blocker”: it is a wide-spectrum blocker — which happens to be able to function as a mere “ad blocker”. The default behavior of uBlock Origin when newly installed is to block ads, trackers and malware sites — through EasyList, EasyPrivacy, Peter Lowe’s ad/tracking/malware servers, various lists of malware sites, and uBlock Origin’s own filter lists.
uBlock Origin (or uBlock₀) is not an ad blocker; it’s a general-purpose blocker. uBlock₀ blocks ads through its support of the Adblock Plus filter syntax. uBlock₀ extends the syntax and is designed to work with custom rules and filters. Furthermore, advanced mode allows uBlock₀ to work in default-deny mode, which mode will cause all 3rd-party network requests to be blocked by default, unless allowed by the user.
That said, it’s important to note that using a blocker is NOT theft. Don’t fall for this creepy idea. The ultimate logical consequence of blocking = theft is the criminalisation of the inalienable right to privacy.