Microsoft Anti Spam Software I Have My Internet Explorer Homepage Set To Http://www.yahoo.com; Why Am I Now Getting A False "security" Site

I have my Internet Explorer homepage set to http://www.yahoo.com; why am I now getting a false "security" site - microsoft anti spam software

Instead of opening my browser on my site, http://www.yahoo.com, a type of malware is changing on my homepage http://www.atotalsafety.com, and I am constantly pop-up messages in me download the security software (anti-spyware, anti-adware, try looking for spyware protection against spam, etc..) I very latest version of Norton AntiVirus was installed and in operation as well as a screening tool malicious software from Microsoft, but no program will detect this malicious software described above. Has anyone else had this problem and if so, how can it be solved?