If you notice that the browser homepage and the search engine are changed to https://search25.co/, it means that most likely your browsers are infected with a browser hijacker. The hijacker is a type of malware that comes to the computer without the user's consent. Externally, Search25.co looks like a legitimate search engine that improves search efficiency.
According to unscrupulous developers, Search.yourinstantspeedtest.com is a search engine with fast Internet connection speed test functions, as well as functions of similar search pages, namely increasing browsing experience, search efficiency and much more. Indeed, it looks like Yahoo, Bing, Google and other popular search engines.
At first glance, it may seem that Search.searchm3p.com is a legitimate and useful search page with functions for quickly switching to popular online shops, parcel tracking resources, and other popular and simplified sites.
Private.myquicksearch.online is a browser hijacker that changes the home page and the default search engine in your browsers installed in the system (chrome, Mozilla, IE, Edge and so on). The hijacker constantly redirects the user to the search page, which looks similar to legitimate analogs, moreover, offers the possibility of surfing in incognito mode, leaving no traces. In reality, Private.myquicksearch.online is not so good and useful.
Pdfmaster or Pdfmaster.net affiliated with Smallpdf.com is a search provider, which, despite smart design and useful functions may be classified as potentially unwanted program. It's because Pdfmaster.net has own search engine and collects and shares users personal data for commercial purposes.