Free software gives users a chance to protect themselves from malicious software behaviors. Even better, usually the community protects everyone, and most users don't have to move a muscle. Here's how.

Once in a while, users who know programming find that a free program has malicious code. Generally the next thing they do is release a corrected version of the program; with the four freedoms that define free software (see http://www.gnu.org/philosophy/free-sw.html), they are free to do this. This is called a "fork" of the program. Soon the community switches to the corrected fork, and the malicious version is rejected. The prospect of ignominious rejection is not very tempting; thus, most of the time, even those who are not stopped by their consciences and social pressure refrain from putting malfeatures in free software.