Login Error - Microsoft authentication package v1

[Buriim]

How to fix logon failure error. I am getting a error that unknown username and bad password. The same account was working before. The problem is related ot
MICROSOFT_AUTHENTICATION_PACKAGE_V1_0. I found the port which was associated with the login. It is port number 25. But not aware that why it is giving this kind of error on the screen. I need some help here. It looks some kind of virus attack in the system.

[HudSon]

There can be some kind of security risk with the system. You can find the details inside event log. There is more information listed in the same. It is necessary that you must first check out the kind of error in it and then go ahead for the troubleshooting. You are right on your place that some kind of attack in the system can cause such failure. Try to run a full system antivirus scan and then check back. Later on your can go with password policy configuration and then move ahead.