login passwords

well i was just thinking about how computer compares the passwords and stuff
well im sure computer stores the operating system login passwords somewhere ,is there a way we can read them and if there is can we protect them from not being read

well it depends what OS we are talking about here buddy. Please provide more information on the os you are talking about , then i'll try and help you out.

It depends on which OS you are talking about...

linux stores in more than one place... but the passwd file is the OS /etc/passwd
those are encrypted but they are still vulnerable
you can shadow it and it will be harder to access/crack w/o root access /etc/shadow

http://www.tldp.org/LDP/lame/LAME/li...e-formats.html

for windows learn about the SAM file (Security Account Management)

http://www.labmice.net/Security/passwordsec.htm

there is tons more out there.. so if you have any specific questions... search around and then ask what you don't understand

well lets take windows xp and windows 2000

thank you phishphreek sites seem really intresting ill try reading them and come back to you with my questions

XP and 2000 have their SAM files phishphreek80 has given a helpful link in this regard

Xp and 2000 use a one way encryption I believe. You enter a password and from there the compter encrypts it, then everytime you enter a password it encrypts what you enter adn cmpares that to the real password. There is no program that i know of that can decyphire the password files, there are programs how ever that can get passwords other ways, such as LC4 or many other brute force password crackers.

Pretty much all modern operating systems (windows 2000/XP, *NIX) use one way encryption to store passwords now. What one way encryption means is that the password that the user types in is encrypted using the same key that was used to encrypt the stored password and the encrypted password is checked with the encrypted stored password. Thus, the password is never (and cannot be) decrypted.
Cheers,
cgkanchi

You forgot to mention the salt. In most password encryption schemes, the same password and key would only generate the same hash if the salt was also the same. Luckily, MS always uses the same salt (at least in past windows vers, I am not sure about the XP's).