Palo Alto Networks has discovered a previously unknown remote access Trojan (RAT) that has been active for over two years. It has a very low volume in this two-year period, totaling roughly 27 total samples. The malware is delivered via an innovative and unique technique: a downloader we are calling Carp uses malicious macros in Microsoft Excel documents to compile embedded C# (C Sharp) Programming Language source code into an executable that in turn is run to deploy the Cardinal RAT malware family.