Microsoft's and Adobe's software are still some of the biggest targets of malware development, but recently discovered Trojans for Apple's Mac OS X and the Android smartphone platform indicate signs that the bad guys are branching out to other increasingly popular product platforms.

Researchers at Sophos over the weekend revealed that they had discovered a new crimeware kit for a remote access Trojan built specifically for Mac OS X: The so-called BlackHoleRAT, currently in the development phase, appears to be a spin-off of a Windows Trojan known as darkComet. Meanwhile, Symantec researchers today provided details on a new Android Trojan called Android.Pjapps that has been found in legitimate Android apps and that builds a botnet.

Security experts say the new OS X and Android Trojans in and of themselves aren't as significant as are the targets in which they are aimed.

Chester Wisniewski, senior security adviser for Sophos, says SophosLabs used to see only about one piece of malware a week for Mac OS X, but in the past year or two it sees more than one per day. But putting that into perspective, it sees 90,000 new malware samples daily for Windows, he notes.

"Compared with Windows, that's [still] a trickle," Wisniewski says. "But [that's what] makes a Mac more appealing [to cybercriminals]: Its users feel invulnerable because they are confident there aren't many viruses for the Mac, so they don't need to worry."

But Marc Maiffret, founder and CTO at eEye Digital Security, says he sees Android as a bigger target in the next year or two than OS X. "It is a rather basic backdoor and probably not indicative of any major shift or explosion about to happen as far as Mac OS X systems being targeted more by attackers. It is interesting in that I think there is probably a higher chance for Android to be targeted more in the next year or two than Mac OS X itself," Maiffret says.

Even so, it's easy to add new backdoors and exploits to exploit toolkits these days. "And I think you will continue to see more exploits/backdoors both for Mac OSX and Android added to these things in an organic way, but not with the same sense of urgency as we see with Microsoft and Adobe," he says.

The so-called "BlackHole RAT">Trojan crimeware kit Sophos found so far can put text files on the desktop and shut down, restart, or force a desktop into the "sleep" mode. It also can run shell commands, and force user to reboot with a full screen window that only lets them reboot, and it provide a phony administrator password window for phishing, and can send URLs to a client machine.

"The difference with this is that it's a bit more sophisticated and easier to use than most other [Mac OS X]" kits, Wisniewski says. "This is specifically for Mac with an easy graphical user interface and it has a lot more capabilities."

Whether it's a full-blown banking Trojan so far is unclear, however. "It's hard to speculate," he says. But it can grab and delete files and provide the attacker full control of the victim's machine, he says.

The big difference between this BlackHole RAT crimeware kit and an existing one for Windows is that it does not include remote screen control, he says. "The Mac version doesn't do that yet ... But it's still in development ... and it seems [the developer] plans to add more advanced capabilities," Wisniewski says. "It looks like an experiment or a thought exercise on whether he can develop an advanced, multifunction Trojan like the one for the Windows platform."

Meanwhile, the Android.Pjapps Trojan can install apps, go to websites, add bookmarks to a victim's browser, send text messages, and block text-message responses. Symantec has found it infecting the legitimate Steamy Window App, which "steams up" the phone's screen and lets the user wipe it off.

"Android malware is on the rise. Android.Pjapps is another example of a Trojan with backdoor capabilities that targets Android devices," Symantec researcher Mario Ballano blogged today. "As seen with previous Android threats, it is spreading through compromised versions of legitimate applications, available on unregulated third-party Android marketplaces."

Vikram Thakur, principal security response manager at Symantec, says the Android.Pjapps code can easily inserted into any number of otherwise legitimate apps by someone who knows what they are doing. "The Steamy Window app is just one of the many apps out there that we know have been compromised with this code," he says. "We also expect to see quite a few more legitimate looking apps over the coming days propagating this threat via unregulated Android marketplaces."

eEye's Maiffret says Mac systems still have more valuable data to target than Androids. "I don't know if Android is a bigger target just yet because Mac systems will still have more data that attackers care to get after," he says. "I think once Android devices, particularly in the U.S., have wide adoption of NFC [near-field communication] technology for wireless payment then we will see some really interesting things start to happen."

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