A hook_user() implementation could do that.

If you are actually looking to block spammers, you might check the email_verify module to block people without valid email addresses. That will probably be more effective.

Nancy

Injustice anywhere is a threat to justice everywhere. -- Dr. Martin L. King, Jr.

From: Jarry
I'm looking for a possibility to restrict login names
during registration, i.e. I want to forbid using strings
"abc" or "ABC" on whatever position in the login names
they pick. How could I do that?