If you don't have any username password, then the only way to recover the password for IDS-4215 is to reimage the device.

If you had service account username/password, you might have logged in as the service account, su to root, then enter "passwd (user)" to reset a user's password.

Assuming that you dont have any username/password, On a 4215 (and also on 4210, 4220, 4230, 4235 and 4250) you can connect to the serial console, reboot the sensor, then when the Grub menu appears, select "Cisco IDS Recovery", choice 1 on the Grub menu. When this process completes, all user data on the sensor is lost. The system is restored back to the default state, except that the network settings are remembered. All accounts are deleted except for the single administrative account "cisco", whose password is reset to "cisco".

You'll need system image file to perform this operation. You may download these from following links given that your CCO ID has sufficient privileges-

IPS 5.x System Files

http://www.cisco.com/cgi-bin/tablebuild.pl/ips5-system

IDS 4.x System Files

http://www.cisco.com/cgi-bin/tablebuild.pl/ids4-app-recovr

You can refer to readme files available on above links for detailed instructions to perform reimage.

Hope this helps.

Regards,

Vibhor.