I got 3 more "tester-type" samples and added them below - in addition to the well known 4 samples mentioned by Seculert.
You can read more about it here:
Seculert Dexter - Draining blood out of Point of Sales
TrendMicro Infostealer Dexter Targets Checkout Systems
Verizon: Dexter: More of the same, or hidden links?
Volatility labs Unpacking Dexter POS "Memory Dump Parsing" Malware
Trustwave labs: The Dexter Malware: Getting Your Hands Dirty
Symantec Infostealer.Dexter