To prevent malware from being installed in Mozilla Firefox, you need to perform these simple tasks: Make sure not to download any pirated software or applications. Be extra careful while downloading freeware or shareware applications. To protect the browser make sure you have an anti-spyware and antivirus application installed. Always download the latest security patches to the applications. These are some of the steps you can take to prevent malware from being installed in Mozilla Firefox. For further assistance, you can contact Mozilla customer support number.