Possible Clues:

• Shibboleth
• Security protection
• "123456" is a weak one
• Fool should follow parking information -- it's needed to get in
• Idiot returned steel key
• Security input
• Step over weapon that's required by sentry
• Send message, one maybe stolen by 21
• Don't answer the questions for first four characters in 6 down - it's an issue of security
• Log-on need