Umm well rest assured it's not due to
FE 
Its basically mostly due to some software you have installed or sometimes some sites try to install software by opening popups and asking you to install stuff to continue.
Always be careful about what "you install".
I also suggest you use a good antivirus and firewall pack that will take care of such issues. A good
paid alternative is
ESET Smart Security Suite
While if you want something
free, you can use
Avira Antivirus and a good free firewall. For novice users, i suggest
Zone Alarm.
All the above are personally tested, industry leading software and perfectly safe.
In your case, you can also install this software:
Ad-Aware Free - Download security software for spyware removal - Lavasoft
Its free and will scan and remove any keyloggers and such programs from your computer.
Having said that, i would suggest you invest in a full antivirus+firewall suite i mentioned rather than a temporary stop gap solution
