When i first downloaded malwarebytes free trial version when i first opened up computer through firefox it would block the www-search.info browser hijacker.I couldnt afford to buy premium so i uninstalled and reinstalled free version now it wont block this hijacker.
the free version doesn't have real time protection, so it can't block anything. when you installed the free version, it gives you an option to try out the full version for free (a trial) after which it will revert to the free version (unless you pay). the full version has real time scanning/protection. you likely signed up for the trial which later expired.
solution. with malwarebytes, it is an excellent demand scanner. use it for that. (or pay if you wish real time protection also). but if you don't wish to pay, download winpatrol (the free version). it has real time protection for browser hijackers and home page protection.