ScanQuery is installed due to oversight in most of the instances. It conforms to requirements to legitimate software, but that is rather a marginal case closer to malware than to useful software.
A user is notified of its delivery, but fails to pay attention as the program is a part of free download comprising multiple objects, most of which are extremely desirable. That is how the program is swallowed in most of the cases.
The point of the issue is that the program adds its toolbar to browser window. It also replaces current home page to its own, scanquarry.com. The page is a search page that has actual search tool in its disposal, but the search area is extremely restricted and obviously covers only websites promoted by persons related to the program.
Many users are not happy to use this search engine and are keen to get rid of ScanQuery issue. The manual guide for ScanQuery removal is provided below, other system security and privacy issues can be detected and fixed by free scanner available here.