A new trojan affecting OS X has been discovered by security firm F-Secure, disguising itself as a PDF and setting up a backdoor in a Mac user’s hard drive after displaying Chinese characters (shown above) once executed. The backdoor, at this point, isn’t much of a threat as it doesn’t currently do any harm, although that could change at any time at the discretion of the trojan’s creator(s).
If you happen to run into this trojan during your daily web browsing, the positive side is that it will be quite easy to identify; the PDF in which the trojan is embedded does not currently have an icon, distinguishing it from ordinary PDF files. However, the trojan could become embedded in another file type with a familiar icon, so it is still best to be cautious when opening any files that seem suspicious or come from an untrusted source.
Always exercise caution when downloading suspicious files, and scan files for viruses whenever necessary to prevent becoming infected with this and any other virus.