I will break down in a diagram of the EBOOT handlers security:

KNOWN SECURITY LOOPHOLES
<icon0>
<icon1>
<pic0>
<pic1>
<param.sfo>
<snd0.at3> (Some reports say)

PSP BOOTUP SECURITY CHECK

param.sfo > data.psp > data.psar

So on 2.5 the sfo stage is the only one passed, the the psp recognizes it has the familiar data.psp file (I'm not quit sure how...)

so I'll explain each files purpose

param.sfo (tells psp how to use a file)
data.psp (runs an updater applet)
data.psar (is a container for the updates files to be flashed

Anyone can break the sfo stage at this point with a few tools, or hell even with notepad.

But of course their are always loopholes so i will show which ones are on each version:

HOMEBREW - 1.0, 1.5
OVERFLOW - 1.0, 1.5 1.51, 1.52, 2.0, (2.01 and 2.5 are partially affected)
VIDEO EXPLOIT - 1.0, 1.5, 1.51, 1.52, 2.0
...there are more but I just said the top 3

PSP 2.5's cracked file handlers...
eboot handler (I say again partially no code running yet)

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