The trojan (called Trojan.PWS.ChromeInject.A) is disguised as the GreaseMonkey add-on to Firefox.  It uses javascript to identify bank and money transfer website logins and passwords; subsequently sending the information to a Russian website.

Its path onto PCs is via downloads of fake GreaseMonkey add-on software and as a 'passenger' with downloads of unsigned / unverified software.  It starts to gather information as soon as the browser is opened.

The advice is only to download GreaseMonkey from known safe sites and to be very cautious about downloading unsigned / unverified software. 

Firefox is probably been targeted because a larger percentage of internet users are now using it as they standard browser.

Living Streams comment:  It is our recommendation to never store bank logins / passwords in browsers.  It is also good practice to use the master password feature within Firefox.