Cracker on my forum

[Sir Osis of Liver]

From what Arantor posted, replacing all older passwords with 60 char hash should be your best option.  It will have the desired effect of removing all the older MD5 and SHA1 passwords and require reset for affected members.  Blanking the field works on test install, but sounds like it's a bad idea from mysql's standpoint.

[Arantor]

Empty should be fine if I remember rightly. Haven't tested it in a long time.