Good program for practicing hacking?

[StackMasher]

I'd like a good program to practice finding and using vulnerabilities. Preferably open source so I can see a bit clearer what the writer did wrong once I'm done.

 

[FAST6191]

Using is any virtual machine (or full machine if you have the space and desire) and a trip to http://www.oldversion.com/ . I have seen some whole linux distros and similar packed with old software and iffy security so you can
What you fire them from is up to you. The start for most is probably kali linux though, https://www.kali.org/ . There are others https://www.concise-courses.com/linux-distros/

Finding. I guess I will say look up things called hackmes. Various ones exist for web and desktop (and possibly mobile, never looked there) and will have writeups as to what goes, unless you are doing the current ones that have not been solved yet.

Beyond that it will depend what you want to hack -- IDA ( https://www.hex-rays.com/products/ida/ ) is a wonderful program almost without equal for hacking X86 (and a lot of embedded) stuff but not much cop for doing web stuff.