Script injection on all browsers

Question

I have something injecting a script into all web browsers that I have tried - Firefox, IE, Edge, Chrome - and it doesn't look like an extension (since it is doing so in different web browsers). I suspect it's either a process injection or some silent process doing the work, but cannot pinpoint it. Can anyone advise what I should look for?

It appears it does an injection into newtab-serviceworker.js as well, changing its search form to its own. Bugga! This is the code from that file:

var EXTRA_FILES = [
  "/xjs/_/js/k=xjs.ntp.en_US.iCI9PQB5wew.O/m=jsa,ntp,d,csi/am=BA/rt=j/d=1/t=zcms/rs=ACT90oFcUbquz13KP289MZy7OI9wPcMXiA",
];
var CHECKSUM = "r4v3sd";

var BLACKLIST = [
  '/gen_204\?',
  '/async/',
];

var FILES = [
  '/images/srpr/logo11w.png',
  '/images/srpr/chrome_ntp_white_logo2.png',
      '/' + '/ssl.gstatic.com/chrome/components/doodle-notifier-01.html'
].concat(EXTRA_FILES || []);

var CACHENAME = 'newtab-static-' + CHECKSUM;

self.addEventListener('install', function(event) {
  event.waitUntil(caches.open(CACHENAME).then(function(cache) {
    return cache.addAll(FILES);
  }));
});

Answer 1

I've figured out that it was an in-built Chrome search toolbar that was enabled, that I have mistakenly taken for a virus/malware. Thanks out to those who deserve it.

Answer 2

Some viruses will inject themselves into each major browser, by extension or other means, as each browser operates differently. Seeing ads on pages where they don't belong (i.e. your New Tab page should not have any ads, neither should many major websites) is a clue that you may have a virus on your computer.

If you cannot come up with a legitimate explanation for this happening (i.e. you installed an extension in just one browser), you should assume you have a virus.

It is possible the virus is doing other things as well. (i.e. logging any credit card numbers you type in, or spamming all your friends email accounts) It is also possible that the virus will be commanded to take further action at a later time. (ransom-ware)

The best way to eliminate viruses is to completely wipe the operating system.
(backup your personal files first!)

A less thorough approach is to simply install and run an anti-virus program. However (unlike a complete wipe of the OS) an anti-virus program cannot guarantee complete successful removal of the virus.

If you have been using a non-administrative user account on your computer, it is possible the virus is contained in that account and you can simply switch to a new account. However, this is not the default setup for most people.