You design your system

[Fabiano_Pessoa]

For better be your antivirus, two problems occur frequently:

Lack of update.
Inefficiency to block changes in the registry keys or writing to the system folder.
For malware to install itself on the system successfully it needs basically two things, run and allowed to spread. Many users do not know, but as an administrative user, you have the power to destroy your system if you wish, as well as install whatever you want on it. When working on a computer as an administrative user, everything the user does is run with administrative powers and as such, you can modify any part of the operating system.

hugs