We recently came across what appeared to be a new sample, but was actually part of malware discovered in 2010. This new-old sample is built from publicly available source code and, like many of its kind, is frequently rebranded. Because of all the changes that malware authors have made, we have detection for each customized iteration. One such iteration (SHA1 8d81462089f9d1b4ec4c7423710cf545be2708e7) is commonly deployed under private obfuscators (such as H1N1 or Umbra). We detect this threat as TrojanSpy:Win32/SSonce.C(the sample also has a message for antivirus researchers, asserting that our job is monotonous and boring.)
Other backdoors that originate from the same source code are currently detected as Backdoor:Win32/Bezigate.A and Backdoor:Win32/Talsab.C, and Backdoor:Win32/Nosrawec.C. What we are seeing here is rampant use of copy/paste in the code. Because of this, all these spying families share common features, such as: reverse-connection to an attacker's server, plugins capable of file transfers, screen capture and anti-virus software disabling. Although the code is publicly available, there are some features, such as mouse/keyboard control, which are only available in private versions, as seen from the Facebook page of one of the authors.
A high number of version builds and obfuscator updates is characteristic of these types of threats, as the malware authors are constantly struggling to bypass our scanner's detection.
So essentially, because antivirus researchers are doing their job well, malware authors have to copy/paste code over and over again. Well, we think that's boring.