A new variant of the Flashback Trojan is infecting Macs, says security firm Intego. Dubbed Flashback.G, the malware is reported to use three different methods to try and infect a Mac. The first two involve Java vulnerabilities, which are stopped if a computer's Java installation is up to date. If a system has an outdated version of Java however, the Trojan may be able to install itself without a chance to intervene.