When you enable FilterKeys, you are presented with the following dialog:

Do you want to save the current settings as the default for new users and the login prompt?

If you choose Yes, FilterKeys are be enabled during a logon session.
If you select No, FilterKeys are enabled for your profile only and the login prompt is not affected.

If FilterKeys are enabled during a logon session:

1. Press and hold the CTRL key until the system beeps twice (the default is 1 second).

2. With the CTRL still depressed, hold down the ALT key until the system beeps twice.

3. Still holding CTRL and ALT, press DEL until the password prompt is displayed.

4. Hold down each key of your password for 2 beeps, until the * indicates the key has been entered.
    If you need to use the SHIFT or CTRL, hold these for 2 beeps, before pressing the 2nd key.

5. Use the mouse to click OK, when your password is completely entered.

Once you logon, use Control Panel / Accessibility to uncheck the FilterKeys check box. Click OK. When prompted with:

Do you want to save the current settings as the default for new users and the login prompt?

click Yes.

You may now enable the FilterKeys for your profile only.