Steve-O -- Challenges Hackers ... Come Get My Dong Pics!

Steve-O is putting his nuts on the line -- boldly challenging the hackers behind the nude celebrity leak to expose new photos of his junk.

Steve-O tells us he has lots of uncensored pics of himself showing off his junk -- trust us, some are more graphic than these -- and he's storing them on iCloud. He just tweeted a challenge to the hackers to come and get his stash ... if they're good enough.

As we first told you ... a lot of male celebs are taking steps to protect their photos because they're worried the hackers will start targeting dude nudes soon.

As usual, Steve-O -- and his frank and beans -- are going against the grain.