It is a relatively new and dangerous kind of threat and maybe your anti-virus applications can not detect it. If you see new toolbars in your Mozilla or Internet Explorer and you didn't intentionally installit, or you keep getting pop-up windows at your internet browser contained unwanted ads and causing your browser often crashes, or if you browser's start page has changed without your knowing, big probably you infected by spyware/adware.
Even if you don't see anything, you may be infected, because more and more spyware is hide smart and silently tracking your surfing behaviour to create a marketing profile of you that will be sold to advertisement companies.
To prevent or remove malware and adware from internet browser, we need good anti malware which having capability to protect and clean our browser from adsware, keylogger, malware, and spyware..
And here is some free anti adware, which you can download and use it free for forever (non trial)
ANVI SMART DEFENDER
Fight against malicious software, such trojan, spyware, adware, keylogger, bots, etc.
It is free to use, having real time protection against threat, and have smart scan engine.
Malware and adsware detection very good, but sometime will detect non malware as threats.
MWAV TOOLKIT UTILITY
Mwav Toolkit Utility will scan your computer from trojan, malware, spyware, adware, keylogger, virus, sniffer, dialer, etc.
Best of it,, it's free and no need installation, a.k.a portable anti malware.
But since it is portable anti malware, it doen't have realtime protection. So not recommended to use as primary anti anti malware program, but useful as remover for already infected computer.
NORTON SECURITY SCAN
Famous security software. This Norton Security Scan come to protect yours computer for free. It give protection to malware, adware, trojan and spyware. Just download it for free.
SUPERANTISPYWARE PORTABLE SCANNER
Anothers portable anti spyware, malware, and others dangerous program, and since it is portable, so no realtime protection. But is is free, so useful for you if yours computer/browser infected by spyware, or adware and want to clean it.
IOBIT MALWARE FIGHTER
This anti adware software is combination of anti malware and anti virus, free license, and have realtime protection. And also update daily.
It claimed have "Dual-Core" anti-malware engine, to detect complex and deep malware, like spyware, adware, trojans, keyloggers, bots, worms, and hijackers. Come with browser protection module, IObit Malware Fighter will full protect online surfing & privacy protection by blocking the malicious pop-ups, reducing homepage hijacking and removing malicious toolbars/plugins.
SPYBOT SEARCH & DESTROY
This free version software is so powerful to remove any spyware, trojan, adware, and others dangerous malware. It come with regular update, and many option to choose, from quarantine, log report, system backup, etc. but some option only can be used at paid version. However this software is popular and top rated at many others website out there to remove spyware/adware.