Apple's Snow Leopard update for Mac OS X ships later this week, but compatibility and security worries have already arrived.

Adobe on Tuesday confirmed that its Creative Suite 4 (CS4) line of products is compatible with Snow Leopard, except for Adobe Drive/Version Cue. It also acknowledged that its older CS3 software has not been tested with Apple's forthcoming operating system.

In an effort to dispel worries that CS3 users would be unable to use their software if they upgraded to Mac OS X 10.6, Adobe Photoshop product manager John Nack subsequently clarified in a blog post that "No one said anything about CS3 being 'not supported' on Snow Leopard."

He stopped short however of declaring that CS3 will be fully functional under Snow Leopard, leaving Adobe users who haven't upgraded to CS4 wondering, like Microsoft Office 2004 users, whether any show-stopping glitches await.

An unofficial, community-compiled Snow Leopard application compatibility list was briefly available at http://snowleopard.wikidot.com/, but the hosting site appears to have been overwhelmed by the visitor traffic and was returning a blank page at the time this article was filed.

With regard to security, Trend Micro said that one its researchers had discovered several Web sites advertising free copies of Snow Leopard. What's actually offered is malware, specifically, a DNS changing Trojan known as OSX_JAHLAV.K.

"Once executed, OSX_JAHLAV.K decrypts codes, which include a script that downloads other malicious scripts," said Trend Micro's Bernadette Irinco in a blog post. "The said script then alters the DNS configuration and includes two additional IP addresses in its DNS server. Users are thus possibly redirected to phishing sites and other fraudulent sites. In fact, some of these bogus sites are reportedly hosting FAKEAV (rogue antivirus) variants and components."

According to Trend Micro, OSX_JAHLAV.K may be downloaded without the user's knowledge following a visit to a malicious Web site. The Trojan, however, has a "low" overall risk rating.

Foxit Corporation, which makes the PDF reading program Foxit for Windows, Linux and various mobile platforms, on Tuesday warned that hackers are distributing software that purports to be Foxit Reader for Mac, a product that hasn't been released yet.

Sophos, a security company, says that the software that claims to be "Foxit Reader for Mac" is really the Jahlav Trojan.

Apple claims that 64-bit applications running on Snow Leopard are more secure than 32-bit versions because of a better function-passing mechanism, hardware-based execution control for heap memory, and stronger checksums for preventing memory corruption attacks.

Late builds of Mac OS X 10.6 also reportedly included malware scanning capabilities.

Apple has cited the scarcity of Mac malware a point of differentiation with Windows PCs in its marketing material. A recent Apple TV commercial suggests that Mac users don't face the same virus worries as PC users. In keeping with that position, Apple last December removed an old support Web page that suggested the use of multiple antivirus applications to keep Macs secure.

An Apple spokesperson at the time explained the decision thus: "The Mac is designed with built-in technologies that provide protection against malicious software and security threats right out of the box. However, since no system can be 100% immune from every threat, running antivirus software may offer additional protection."

Choosing not to visit shady Web sites in search of free software may offer a similar measure of protection.

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