Disabling the Ctrl+Alt+Del security attention sequence can compromise system security. Because only Windows responds to the Ctrl+Alt+Del security sequence, you can be assured that any passwords you enter following that sequence are sent only to Windows. If you eliminate the sequence requirement, malicious programs can request and receive your Windows password. Disabling this sequence also suppresses a custom logon banner.

A malicious user might install malware that looks like the standard logon dialog box for the Windows operating system and capture a user's password. The attacker can then log on to the compromised account with whatever level of user rights that the user has. It's best practice in a secure environment to force the use of CTRL+ALT+DEL.