No antivrus program is 100% full proof against all the different variations of malware and spyware,etc. This stuff can come from anyware that one surfs the internet. It can come in on a pop up ad, it could come in from reading about the local weather, etc. or opening an email attachment. My best recommendation is to keep all security updates from Microsoft current. I beleive they are releasing a bunch of them on April 13th. It is a good idea to have a few other programs at your disposal for dealing with this stuff. Malwarebytes and SuperAntispyware are excellent programs and I have used both for years. There is also a few online scanners that I use occasionally as well. Windows Live One Care Scanner and the Free Eset Online Scanner. Additional information from McAfee can be found by going to the Security Awareness Community.