Well with the first PSP Virus being released its a good thing we have Dark Killers scanner that checks for suspicious code, heres the scoop from the readme:
PSafeP 1.1
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By: Dark Killer
About:
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PSafeP is a windows tool to scan Sony PSP executable (EBOOT.PBP) files for suspicious code.
Changelog:
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v1.1:
-program now attempts to decipher between read and write access to the flash memory
-PBP file validation
-some small misc tweaks