Make sure to update your Computer(s).
Wether PC or even a Mac
a Computer that hasn’t been updated can be exploited.
See the article below from CRN.
Mac without the latest Java update can be compromised while visiting a malicious Web site or one that contains a poison link secretly installed by a criminal. Clicking on a malicious link can run code through Apple Safari and Mozilla Firefox browsers without the user knowing. Flashback is designed to steal passwords to online banking and other Web sites, experts say.
via Second Security Firm Finds Massive Mac Infection