Mac owners have a new variant of an old trojan to keep an eye out for, but it actually sounds fairly easy to avoid.
It seems that the Flashback trojan horse has returned to the world of Macs, but with a new variant known as Flashback.g. According to security firm Intego, the new variant is a bit more devious than previous versions as it attempts to present you with a security certificate like the one you see above that claims it is from Apple. Once installed the trojan will inject itself into your Web browsers and networked programs like Skype searching for user names and passwords for sites such as Google, PayPal and banks.
The issue with this particular virus, however, is that it takes a lot of special circumstances for the the attack to work: You need to be running an outdated version of Java and you also must not have any anti-virus protection of any kind installed. The former is super easy to take care of by running a system update check on your Mac, and the latter is an attempt by the malware makers to continue to fly under the radar. If Flashback.g does manage to install itself, it is fairly easy to determine you have it as it will cause networked programs to become unstable and crash as it will interfere with their processes.
As you should already know, just make sure to keep your system up to date, and be careful about where you download programs from and this should be a fairly easy threat to avoid.