The fact that the initial version of malware was completely unencrypted and now with simple string replacement made me believe the whole thing was created by some kids with fairly basic programming skills, not by pros. Almost all modern day PC viruses & malwares encrypt their payloads to avoid detection by AV software.
Update: c0d3m4st4 (https://twitter.com/c0d3m4st4) just added safety check to his VPKTool utility program: https://twitter.com/c0d3m4st4/status/782395624037711872.
There were two malicious dumps submitted to /r/VitaPiracy on reddit recently that can permanently brick Vita. It basically remounts os0 and vs0 as read/write and then wipes out their contents which contains Vita's OS. The two malicious dumps are "Fruit Ninja [uS] [TESTED] [MAIDUMP]" and "kung fu rabbit - tested working - maidump v233.2z8".
/r/VitaPiracy has issued a warning here: https://www.reddit.com/r/VitaPiracy/comments/55farx/community_warning_there_have_been_two_separate/
Reddit user "realshotgun" provided a simple way to check new dumps for suspicious behavior for the time being:
This is essentially the first Vita malware and will for sure evolve in the future to make detection even harder, such as encrypting the malicious payload. All Henkaku users should be aware and get homebrew & game dumps from reliable sources.