ESET analyzes multiple samples targeting OS X every day. Those samples are usually potentially unwanted applications that inject advertisements into browser displays while the victim is browsing the web.
For the last few weeks, we have been investigating an interesting case where the purpose of the malware is to steal the content of the keychain and maintain a permanent backdoor. This article will describe the components of this threat and what we know about it so far.
It is still not clear how victims are initially exposed to OSX/Keydnap. It could be through attachments in spam messages, downloads from untrusted websites or something else.
What we know is that a downloader component is distributed in a .zip file. The archive file contains a Mach-O executable file with an extension that looks benign, such as .txt or .jpg. However, the file extension actually contains a space character at the end, which means double-clicking the file in Finder will launch it in Terminal and not Preview or TextEdit.